fix(sync): normalize log prefixes and S3 prompt UX (#115)

* feat(s3): create bucket interactively during auth when unconfigured

Problem: when a user runs `:Pending s3 auth` with no bucket configured,
auth succeeds but offers no way to create the bucket. The user must
manually run `aws s3api create-bucket` and update their config.

Solution: add `util.input()` coroutine-aware prompt wrapper and a
`create_bucket()` flow in `s3.lua` that prompts for bucket name and
region, handles the `us-east-1` LocationConstraint quirk, and logs a
config snippet on success. Called automatically from `auth()` when
`sync.s3.bucket` is absent.

* ci: typing

* feat(parse): add `parse_duration_to_days` for duration string conversion

Problem: The archive command accepted only a bare integer for days,
inconsistent with the `+Nd`/`+Nw`/`+Nm` duration syntax used elsewhere.

Solution: Add `parse_duration_to_days()` supporting `Nd`, `Nw`, `Nm`,
and bare integers. Returns nil on invalid input for caller error handling.

* feat(archive): duration syntax and confirmation prompt

Problem: `:Pending archive` accepted only a bare integer for days and
silently deleted tasks with no confirmation, risking accidental data loss.

Solution: Accept duration strings (`7d`, `3w`, `2m`) via
`parse.parse_duration_to_days()`, show a `vim.ui.input` confirmation
prompt before removing tasks, and skip the prompt when zero tasks match.

* feat: add `<C-a>` / `<C-x>` keymaps for priority increment/decrement

Problem: Priority could only be cycled with `g!` (0→1→2→3→0), with no
way to directly increment or decrement.

Solution: Add `adjust_priority()` with clamping at 0 and `max_priority`,
exposed as `increment_priority()` / `decrement_priority()` on `<C-a>` /
`<C-x>`. Includes `<Plug>` mappings and vimdoc.

* fix(s3): use parenthetical defaults in bucket creation prompts

Problem: `util.input` with `default` pre-filled the input field, and
the success message said "Add to your config" ambiguously.

Solution: Show defaults in prompt text as `(default)` instead of
pre-filling, and clarify the message to "Add to your pending.nvim
config".

* ci: format

* ci(sync): normalize log prefix to `backend:` across all sync backends

Problem: Sync log messages used inconsistent prefixes like `s3 push:`,
`gtasks pull:`, `gtasks sync —` instead of the `backend: action` pattern
used by auth messages.

Solution: Normalize all sync backend logs to `backend: action ...` format
across `s3.lua`, `gcal.lua`, and `gtasks.lua`.

* ci: fix linter warnings in archive spec and s3 bucket creation

lua/pending/sync/s3.lua

@@ -88,9 +88,7 @@ local function create_bucket()
   end
 
   local region = util.input({ prompt = 'AWS region (' .. default_region .. '): ' })
-  if not region then
-    region = default_region
-  elseif region == '' then
+  if not region or region == '' then
     region = default_region
   end
 
@@ -220,12 +218,12 @@ function M.push()
       os.remove(tmpfile)
 
       if result.code ~= 0 then
-        log.error('s3 push: ' .. (result.stderr or 'unknown error'))
+        log.error('s3: push failed — ' .. (result.stderr or 'unknown error'))
         return
       end
 
       util.finish(s)
-      log.info('s3 push: uploaded to s3://' .. s3cfg.bucket .. '/' .. key)
+      log.info('s3: push uploaded to s3://' .. s3cfg.bucket .. '/' .. key)
     end)
   end)
 end
@@ -247,7 +245,7 @@ function M.pull()
 
       if result.code ~= 0 then
         os.remove(tmpfile)
-        log.error('s3 pull: ' .. (result.stderr or 'unknown error'))
+        log.error('s3: pull failed — ' .. (result.stderr or 'unknown error'))
         return
       end
 
@@ -258,7 +256,7 @@ function M.pull()
       end)
       if not load_ok then
         os.remove(tmpfile)
-        log.error('s3 pull: failed to parse remote store')
+        log.error('s3: pull failed — could not parse remote store')
         return
       end
 
@@ -320,7 +318,7 @@ function M.pull()
 
       os.remove(tmpfile)
       util.finish(s)
-      log.info('s3 pull: ' .. util.fmt_counts({
+      log.info('s3: pull ' .. util.fmt_counts({
         { created, 'added' },
         { updated, 'updated' },
         { unchanged, 'unchanged' },
@@ -416,7 +414,7 @@ function M.sync()
 
       local f = io.open(s.path, 'r')
       if not f then
-        log.error('s3 sync: failed to read store file')
+        log.error('s3: sync failed — could not read store file')
         return
       end
       local content = f:read('*a')
@@ -425,7 +423,7 @@ function M.sync()
       local push_tmpfile = vim.fn.tempname() .. '.json'
       local tf = io.open(push_tmpfile, 'w')
       if not tf then
-        log.error('s3 sync: failed to create temp file')
+        log.error('s3: sync failed — could not create temp file')
         return
       end
       tf:write(content)
@@ -437,13 +435,13 @@ function M.sync()
       os.remove(push_tmpfile)
 
       if push_result.code ~= 0 then
-        log.error('s3 sync push: ' .. (push_result.stderr or 'unknown error'))
+        log.error('s3: sync push failed — ' .. (push_result.stderr or 'unknown error'))
         util.finish(s)
         return
       end
 
       util.finish(s)
-      log.info('s3 sync: pull ' .. util.fmt_counts({
+      log.info('s3: sync ' .. util.fmt_counts({
         { created, 'added' },
         { updated, 'updated' },
       }) .. ' | push uploaded')