chore(bump-plugin-shas): pin to claude-plugins-community a27629fc + add single-plugin `plugin` dispatch target (#3126)

Bumps the bump-plugin-shas action pin to the new claude-plugins-community SHA
(a27629fc) which adds (1) manifest synthesis for strict:false skills-only
externals — so they can finally be bumped instead of drifting — and (2) an
`only` input to target ONE plugin on demand.

Surfaces the targeting as a `plugin` workflow_dispatch input threaded into the
action's `with:` block, so an operator can run:
  gh workflow run bump-plugin-shas.yml --repo anthropics/claude-plugins-official -f plugin=<name>
(e.g. to bump the now-eligible netsuite-suitecloud, a strict:false entry the
old action hard-skipped). Empty `plugin` = unchanged nightly behavior.

The plugin->only->ONLY->bump.sh chain was reviewed (ultra) and e2e-verified live
on claude-plugins-community before this pin bump.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/bump-plugin-shas.yml

@@ -30,6 +30,12 @@ on:
         description: Cap on plugins bumped this run
         required: false
         default: '30'
+      plugin:
+        description: >-
+          Bump ONLY this plugin name (exact entry name; empty = all stale). A
+          frozen/sha-exempt target is still skipped (same as a full run).
+        required: false
+        default: ''
 
 permissions:
   contents: write
@@ -51,11 +57,12 @@ jobs:
 
       # createCommitOnBranch-based bump so commits are signed by GitHub and
       # satisfy the org-level required_signatures ruleset on main.
-      - uses: anthropics/claude-plugins-community/.github/actions/bump-plugin-shas@d207465eb6ec02b6f3f1dbb131717830dc9ecc68
+      - uses: anthropics/claude-plugins-community/.github/actions/bump-plugin-shas@a27629fc8c11488cc3e25ec527bb28196c5db04f
         id: bump
         with:
           marketplace-path: .claude-plugin/marketplace.json
           max-bumps: ${{ inputs.max_bumps || '30' }}
+          only: ${{ inputs.plugin }}
           pr-mode: per-entry
           claude-cli-version: latest