feat(forge): inline overlay rendering for forge links (#126)

* docs: document S3 backend, auto-auth, and `:Pending done` command

Problem: The S3 backend had no `:Pending s3` entry in the COMMANDS
section, `:Pending auth` only mentioned Google, the `sync` config
field omitted `s3`, `_s3_sync_id` was missing from the data format
section, `:Pending done` was implemented but undocumented, and the
README lacked a features overview.

Solution: Add `:Pending s3` and `:Pending done` command docs, rewrite
`:Pending auth` to cover all backends and sub-actions, update config
and data format references, add `aws` CLI to requirements, and add a
Features section to `README.md`.

* feat(forge): add forge link parser and metadata fetcher

Problem: no way to associate tasks with GitHub, GitLab, or Codeberg
issues/PRs, or to track their remote state.

Solution: add `forge.lua` with shorthand (`gh:user/repo#42`) and full
URL parsing, async metadata fetching via `curl`, label formatting,
conceal pattern generation, token resolution, and `refresh()` for
state pull (closed/merged -> done).

* feat(config): add forge config defaults and `%l` eol specifier

Problem: no configuration surface for forge link rendering, icons,
issue format, or self-hosted instances.

Solution: add `pending.ForgeConfig` class with per-forge `token`,
`icon`, `issue_format`, and `instances` fields. Add `%l` to the
default `eol_format` so forge labels render in virtual text.

* feat(parse): extract forge refs from task body

Problem: `parse.body()` had no awareness of forge link tokens, so
`gh:user/repo#42` stayed in the description instead of metadata.

Solution: add `forge_ref` field to `pending.Metadata` and extend the
right-to-left token loop in `body()` to call `forge.parse_ref()` as
the final fallback before breaking.

* feat(diff): persist forge refs in store on write

Problem: forge refs parsed from buffer lines were discarded during
diff reconciliation and never stored in the JSON.

Solution: thread `forge_ref` through `parse_buffer` entries into
`diff.apply`, storing it in `task._extra._forge_ref` for both new
and existing tasks.

* feat(views): pass forge ref and cache to line metadata

Problem: `LineMeta` had no forge fields, so `buffer.lua` could not
render forge labels or apply forge-specific highlights.

Solution: add `forge_ref` and `forge_cache` fields to `LineMeta`,
populated from `task._extra` in both `category_view` and
`priority_view`.

* feat(buffer): render forge links as concealed text with eol virt text

Problem: forge tokens were visible as raw text with no virtual text
labels, and the eol separator logic collapsed all gaps when
non-adjacent specifiers were absent.

Solution: add forge conceal syntax patterns in `setup_syntax()`, add
`PendingForge`/`PendingForgeClosed` highlight groups, handle the
`%l` specifier in `build_eol_virt()`, fix separator collapsing to
buffer one separator between present segments, and change
`concealcursor` to `nc` (reveal in visual and insert mode).

* feat(complete): add forge shorthand omnifunc completions

Problem: no completion support for `gh:`, `gl:`, or `cb:` tokens,
requiring users to type owner/repo from memory.

Solution: extend `omnifunc` to detect `gh:`/`gl:`/`cb:` prefixes and
complete with `owner/repo#` candidates from existing forge refs in
the store.

* feat: trigger forge refresh on buffer open

Problem: forge metadata was never fetched, so virt text highlights
could not reflect remote issue/PR state.

Solution: call `forge.refresh()` in `M.open()` so metadata is
fetched once per `:Pending` invocation rather than on every render.

* test(forge): add forge parsing spec

Problem: no test coverage for forge link shorthand parsing, URL
parsing, label formatting, or API URL generation.

Solution: add `spec/forge_spec.lua` covering `_parse_shorthand`,
`parse_ref` for all three forges, full URL parsing including nested
GitLab groups, `format_label`, and `_api_url`.

* docs: document forge links feature

Problem: no user-facing documentation for forge link syntax,
configuration, or behavior.

Solution: add forge links section to `README.md` and `pending.txt`
covering shorthand/URL syntax, config options, virtual text
rendering, state pull, and auth resolution.

* feat(forge): add `find_refs()` inline token scanner

Problem: forge tokens were extracted by `parse.body()` which stripped
them from the description, making editing awkward and multi-ref lines
impossible.

Solution: add `find_refs(text)` that scans a string for all forge
tokens by whitespace tokenization, returning byte offsets and parsed
refs without modifying the input. Remove unused `conceal_patterns()`.

* refactor: move forge ref detection from `parse.body()` to `diff`

Problem: `parse.body()` stripped forge tokens from the description,
losing the raw text. This made inline overlay rendering impossible
since the token no longer existed in the buffer.

Solution: remove the `forge.parse_ref()` branch from `parse.body()`
and call `forge.find_refs()` in `diff.parse_buffer()` instead. The
description now retains forge tokens verbatim; `_extra._forge_ref`
is still populated from the first matched ref.

* feat(buffer): render forge links as inline conceal overlays

Problem: forge tokens were stripped from the buffer and shown as EOL
virtual text via `%l`. The token disappeared from the editable line,
and multi-ref tasks broke.

Solution: compute `forge_spans` in `views.lua` with byte offsets for
each forge token in the rendered line. In `apply_inline_row()`, place
extmarks with `conceal=''` and `virt_text_pos='inline'` to visually
replace each raw token with its formatted label. Clear stale
`forge_spans` on dirty rows to prevent `end_col` out-of-range errors
after edits like `dd`.

* fix(config): remove `%l` from default `eol_format`

Problem: forge links are now rendered inline, making the `%l` EOL
specifier redundant in the default format.

Solution: change default `eol_format` from `'%l  %c  %r  %d'` to
`'%c  %r  %d'`. The `%l` specifier remains functional for users who
explicitly set it.

* test(forge): update specs for inline forge refs

Problem: existing tests asserted that `parse.body()` stripped forge
tokens from the description and populated `meta.forge_ref`. The
`conceal_patterns` test referenced a removed function.

Solution: update `parse.body` integration tests to assert tokens stay
in the description. Add `find_refs()` tests covering single/multiple
refs, URLs, byte offsets, and empty cases. Remove `conceal_patterns`
test. Update diff tests to assert description includes the token.

* docs: update forge links for inline overlay rendering

Problem: documentation described forge tokens as stripped from the
description and rendered via EOL `%l` specifier by default.

Solution: update forge links section to describe inline conceal
overlay rendering. Update default `eol_format` reference. Change
`issue_format` field description from "EOL label" to "inline overlay
label".

* ci: format

doc/pending.txt

@@ -43,6 +43,7 @@ Features: ~
 - Google Calendar one-way push via OAuth PKCE
 - Google Tasks bidirectional sync via OAuth PKCE
 - S3 whole-store sync via AWS CLI
+- Forge links: reference GitHub/GitLab/Codeberg issues and PRs inline
 
 ==============================================================================
 CONTENTS                                                   *pending-contents*
@@ -68,8 +69,9 @@ CONTENTS                                                   *pending-contents*
  19. Google Tasks ............................................ |pending-gtasks|
  20. Google Authentication ......................... |pending-google-auth|
  21. S3 Sync ................................................... |pending-s3|
- 22. Data Format .............................................. |pending-data|
- 23. Health Check ........................................... |pending-health|
+ 22. Forge Links ........................................... |pending-forge|
+ 23. Data Format .............................................. |pending-data|
+ 24. Health Check ........................................... |pending-health|
 
 ==============================================================================
 REQUIREMENTS                                           *pending-requirements*
@@ -738,7 +740,7 @@ loads: >lua
       max_priority = 3,
       view = {
         default = 'category',
-        eol_format = '%c  %r  %d',
+        eol_format = '%l  %c  %r  %d',
         category = {
           order = {},
           folding = true,
@@ -840,6 +842,7 @@ Fields: ~
                          {eol_format}  (string, default: '%c  %r  %d')
                                     Format string for end-of-line virtual text.
                                     Specifiers:
+                                      `%l`  forge link label (`PendingForge`)
                                       `%c`  category icon + name (`PendingHeader`)
                                       `%r`  recurrence icon + pattern (`PendingRecur`)
                                       `%d`  due icon + date (`PendingDue`/`PendingOverdue`)
@@ -1009,6 +1012,15 @@ PendingFilter       Applied to the `FILTER:` header line shown at the top of
                     the buffer when a filter is active.
                     Default: links to `DiagnosticWarn`.
 
+                                                              *PendingForge*
+PendingForge        Applied to forge link virtual text (issue/PR reference).
+                    Default: links to `DiagnosticInfo`.
+
+                                                        *PendingForgeClosed*
+PendingForgeClosed  Applied to forge link virtual text when the remote
+                    issue/PR is closed or merged.
+                    Default: links to `Comment`.
+
 To override a group in your colorscheme or config: >lua
     vim.api.nvim_set_hl(0, 'PendingDue', { fg = '#aaaaaa', italic = true })
 <
@@ -1443,6 +1455,110 @@ Downloads the remote store from S3, then merges per-task by `_s3_sync_id`:
 `:Pending s3 sync` behavior: ~
 Pulls first (merge), then pushes the merged result.
 
+==============================================================================
+FORGE LINKS                                                   *pending-forge*
+
+Tasks can reference remote issues, pull requests, and merge requests from
+GitHub, GitLab, and Codeberg (or Gitea). References are parsed from inline
+tokens, concealed in the buffer, and rendered as configurable virtual text.
+
+Inline syntax: ~
+
+Two input forms, both parsed on `:w`:
+
+    Shorthand: ~
+        `gh:user/repo#42`       GitHub issue or PR
+        `gl:group/project#15`   GitLab issue or MR
+        `cb:user/repo#3`        Codeberg issue or PR
+
+    Full URL: ~
+        `https://github.com/user/repo/issues/42`
+        `https://gitlab.com/group/project/-/merge_requests/15`
+        `https://codeberg.org/user/repo/issues/3`
+
+Example: >
+    Fix login bug gh:user/repo#42 due:friday
+<
+
+On `:w`, the forge reference stays in the description and is also stored in
+the task's `_extra._forge_ref` field. The raw token is visually replaced
+inline with a formatted label using overlay extmarks (same technique as
+checkbox icons). Multiple forge references in one line are each overlaid
+independently.
+
+The `%l` specifier in `eol_format` is still supported for users who prefer
+the link label in EOL virtual text, but it is no longer in the default
+format (`'%c  %r  %d'`).
+
+Format string: ~
+                                                    *pending-forge-format*
+Each forge has a configurable `issue_format` string with these placeholders:
+    `%i`    Forge icon (nerd font)
+    `%o`    Repository owner
+    `%r`    Repository name
+    `%n`    Issue/PR number
+
+Default: `'%i %o/%r#%n'` (e.g. ` user/repo#42`).
+
+Configuration: ~
+                                                      *pending.ForgeConfig*
+>lua
+    vim.g.pending = {
+      forge = {
+        github = {
+          token = nil,
+          icon = '',
+          issue_format = '%i %o/%r#%n',
+          instances = {},
+        },
+        gitlab = {
+          token = nil,
+          icon = '',
+          issue_format = '%i %o/%r#%n',
+          instances = {},
+        },
+        codeberg = {
+          token = nil,
+          icon = '',
+          issue_format = '%i %o/%r#%n',
+          instances = {},
+        },
+      },
+    }
+<
+
+Fields (per forge): ~
+    {token}         (string, optional) API token for authenticated requests.
+                    Falls back to CLI: `gh auth token` (GitHub), `glab auth
+                    token` (GitLab). Codeberg uses token only.
+    {icon}          (string) Nerd font icon used in virtual text.
+    {issue_format}  (string) Format string for the inline overlay label.
+    {instances}     (string[]) Additional hostnames for self-hosted instances
+                    (e.g. `{ 'github.company.com' }`).
+
+Authentication: ~
+Token retrieval is CLI-preferred, config fallback:
+1. GitHub: `gh auth token` stdout. Falls back to `forge.github.token`.
+2. GitLab: `glab auth token` stdout. Falls back to `forge.gitlab.token`.
+3. Codeberg: `forge.codeberg.token` only (no standard CLI).
+
+Unauthenticated requests work for public repositories. Private repositories
+require a token.
+
+Metadata fetching: ~
+On buffer open, tasks with a `_forge_ref` whose cached metadata is older
+than 5 minutes are re-fetched asynchronously. The buffer renders immediately
+with cached data and updates extmarks when the fetch completes.
+
+State pull: ~
+After fetching, if the remote issue/PR is closed or merged and the local
+task is pending/wip/blocked, the task is automatically marked as done. This
+is one-way: local status changes do not push back to the forge.
+
+Highlight groups: ~
+    |PendingForge|          Open issue/PR link label
+    |PendingForgeClosed|    Closed/merged issue/PR link label
+
 ==============================================================================
 DATA FORMAT                                                    *pending-data*
 
@@ -1481,6 +1597,7 @@ save. This is used internally to store sync backend metadata:
 - Google Calendar: `_gcal_event_id`, `_gcal_calendar_id`
 - Google Tasks: `_gtasks_task_id`, `_gtasks_list_id`
 - S3: `_s3_sync_id` (UUID for cross-device merge)
+- Forge links: `_forge_ref` (parsed reference), `_forge_cache` (fetched state)
 Third-party tooling can annotate tasks via `_extra` without data loss.
 
 The `version` field is checked on load. If the file version is newer than the