feat(forge): inline overlay rendering for forge links (#127)

* 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

* refactor(forge): remove `%l` eol specifier, add `auto_close` config, fix icons

Problem: `%l` was dead code after inline overlays replaced EOL
rendering. Auto-close was always on with no opt-out. Forge icon
defaults were empty strings.

Solution: remove `%l` from the eol format parser and renderer. Add
`forge.auto_close` (default `false`) to gate state-pull. Set nerd
font icons: `` (GitHub), `` (GitLab), `` (Codeberg). Keep
conceal active in insert mode via `concealcursor = 'nic'`.

* fix(config): set correct nerd font icons for forge defaults

doc/pending.txt

@@ -842,7 +842,6 @@ 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`)
@@ -1486,10 +1485,6 @@ 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:
@@ -1505,6 +1500,7 @@ Configuration: ~
 >lua
     vim.g.pending = {
       forge = {
+        auto_close = false,
         github = {
           token = nil,
           icon = '',
@@ -1527,6 +1523,11 @@ Configuration: ~
     }
 <
 
+Top-level fields: ~
+    {auto_close}    (boolean, default: false) When true, tasks linked to
+                    closed/merged remote issues are automatically marked
+                    done on buffer open.
+
 Fields (per forge): ~
     {token}         (string, optional) API token for authenticated requests.
                     Falls back to CLI: `gh auth token` (GitHub), `glab auth
@@ -1551,9 +1552,10 @@ 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.
+Requires `forge.auto_close = true`. 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. Disabled by default. One-way: local status
+changes do not push back to the forge.
 
 Highlight groups: ~
     |PendingForge|          Open issue/PR link label