Add auto-SHA-bump workflow for marketplace plugins

Weekly CI action that discovers stale SHA pins in marketplace.json
and opens a batched PR with updated SHAs. Adapted from the
claude-plugins-community-internal bump-plugin-shas workflow for
the single-file marketplace.json format.

- discover_bumps.py: checks 56 SHA-pinned plugins against upstream
  repos, oldest-stale-first rotation, capped at 20 bumps/run
- bump-plugin-shas.yml: weekly Monday schedule + manual dispatch
  with dry_run and per-plugin targeting options

Entries without SHA pins (intentionally tracking HEAD) are never
touched. Existing validate-marketplace CI runs on the resulting PR.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -0,0 +1,109 @@
+name: Bump plugin SHAs
+
+# Weekly sweep of marketplace.json — for each entry whose upstream repo has
+# moved past its pinned SHA, open a PR against main with updated SHAs. The
+# validate-marketplace workflow then runs on the PR to confirm the file is
+# still well-formed.
+#
+# Adapted from claude-plugins-community-internal's bump-plugin-shas.yml
+# for the single-file marketplace.json format. Key difference: all bumps
+# are batched into one PR (since they all modify the same file).
+
+on:
+  schedule:
+    - cron: '23 7 * * 1'  # Monday 07:23 UTC
+  workflow_dispatch:
+    inputs:
+      plugin:
+        description: Only bump this plugin (for testing)
+        required: false
+      max_bumps:
+        description: Cap on plugins bumped this run
+        required: false
+        default: '20'
+      dry_run:
+        description: Discover only, don't open PR
+        type: boolean
+        default: true
+
+concurrency:
+  group: bump-plugin-shas
+  cancel-in-progress: false
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  bump:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Check for existing bump PR
+        id: existing
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          existing=$(gh pr list --label sha-bump --state open --json number --jq 'length')
+          echo "count=$existing" >> "$GITHUB_OUTPUT"
+          if [ "$existing" -gt 0 ]; then
+            echo "::notice::Open sha-bump PR already exists — skipping"
+          fi
+
+      - name: Ensure sha-bump label exists
+        if: steps.existing.outputs.count == '0'
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: gh label create sha-bump --color 0e8a16 --description "Automated SHA bump" 2>/dev/null || true
+
+      - name: Discover and apply SHA bumps
+        if: steps.existing.outputs.count == '0'
+        id: discover
+        env:
+          GH_TOKEN: ${{ github.token }}
+          PR_BODY_PATH: /tmp/bump-pr-body.md
+        run: |
+          args=(--max "${{ inputs.max_bumps || '20' }}")
+          if [ -n "${{ inputs.plugin }}" ]; then
+            args+=(--plugin "${{ inputs.plugin }}")
+          fi
+          if [ "${{ inputs.dry_run }}" = "true" ]; then
+            args+=(--dry-run)
+          fi
+          python3 .github/scripts/discover_bumps.py "${args[@]}"
+
+      - uses: oven-sh/setup-bun@v2
+        if: steps.existing.outputs.count == '0' && steps.discover.outputs.count != '0' && inputs.dry_run != true
+
+      - name: Validate marketplace.json
+        if: steps.existing.outputs.count == '0' && steps.discover.outputs.count != '0' && inputs.dry_run != true
+        run: |
+          bun .github/scripts/validate-marketplace.ts .claude-plugin/marketplace.json
+          bun .github/scripts/check-marketplace-sorted.ts
+
+      - name: Create pull request
+        if: steps.existing.outputs.count == '0' && steps.discover.outputs.count != '0' && inputs.dry_run != true
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          branch="auto/bump-shas-$(date +%Y%m%d)"
+          count="${{ steps.discover.outputs.count }}"
+          names="${{ steps.discover.outputs.bumped_names }}"
+
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git checkout -b "$branch"
+          git add .claude-plugin/marketplace.json
+          git commit -m "Bump SHA pins for $count plugin(s)
+
+          Plugins: $names"
+          git push -u origin "$branch"
+
+          gh pr create \
+            --base main \
+            --head "$branch" \
+            --title "Bump SHA pins ($count plugins)" \
+            --body-file /tmp/bump-pr-body.md \
+            --label sha-bump