ci: remove Claude mention workflow

Removes the generic Claude mention workflow in favor of more focused,
context-aware workflows already in place.

🤖 Generated with Claude Code (https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/claude-mention.yml

@@ -1,45 +0,0 @@
-name: Claude Mention
-
-on:
-  issue_comment:
-    types: [created]
-  pull_request_review_comment:
-    types: [created]
-  issues:
-    types: [opened, assigned]
-  pull_request_review:
-    types: [submitted]
-
-jobs:
-  claude-mention:
-    if: |
-      (github.event_name == 'issue_comment' && contains(github.event.comment.body, '@claude')) ||
-      (github.event_name == 'pull_request_review_comment' && contains(github.event.comment.body, '@claude')) ||
-      (github.event_name == 'pull_request_review' && contains(github.event.review.body, '@claude')) ||
-      (github.event_name == 'issues' && (contains(github.event.issue.body, '@claude') || contains(github.event.issue.title, '@claude')))
-
-    runs-on: ubuntu-latest
-
-    permissions:
-      contents: read # Cannot merge PR
-      pull-requests: write
-      issues: read
-      actions: read # Required for Claude to read CI results on PRs
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 1
-
-      - name: Run Claude Code
-        id: claude
-        uses: anthropics/claude-code-action@v1
-        with:
-          # See https://github.com/anthropics/claude-code-action/blob/main/docs/usage.md
-          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
-          additional_permissions: |
-            actions: read
-          prompt: |
-            If this is a PR adding a project or library, review against CONTRIBUTING.md criteria.
-            Otherwise, follow the instructions in the comment or issue that tagged you.