ci: switch to commit-message triggers (replace issue_comment)

issue_comment triggers had two problems: Gitea did not reliably fire
them, and the refs/pull/N/head checkout was fragile.  Commit-message
keywords are simpler and guaranteed to work on any push event.

Trigger keywords (add anywhere in the commit message):
  /test-cgal      → CGAL test suite (277 tests, LOW_MEMORY_BUILD)
  /quality-gates  → license/codespell/shellcheck/cgal-conventions
  /docs           → Doxygen build + warning summary
  /links          → Markdown internal link check

test-fast still runs on every push (no keyword needed).

All `issue_comment` event handlers and `refs/pull/N/head` checkouts
removed from all three workflow files.  review/** added to push branch
filters so this PR branch triggers normally.

CLAUDE.md CI table updated.

/test-cgal /quality-gates

.gitea/workflows/markdown-links.yml

@@ -4,13 +4,20 @@ name: Markdown link check
 # file (or anchor).
 #
 # Triggers:
-#   - "/links" as a PR comment  (manual, on the PR branch)
-#   - Weekly cron Mon 05:00 UTC (catches link rot without any PR activity)
-#   - workflow_dispatch          (manual run on any branch)
+#   - "/links" in commit message  (manual, on that exact commit)
+#   - Weekly cron Mon 05:00 UTC   (catches link rot without any activity)
+#   - workflow_dispatch            (manual run on any branch)
+#
+#   git commit -m "docs: rename section /links"
 
 on:
-  issue_comment:
-    types: [created]
+  push:
+    branches:
+      - main
+      - dev
+      - "claude/**"
+      - "feature/**"
+      - "review/**"
   schedule:
     - cron: "0 5 * * 1"   # Monday 05:00 UTC weekly link-rot check
   workflow_dispatch: {}
@@ -20,17 +27,13 @@ jobs:
     if: |
       github.event_name == 'schedule' ||
       github.event_name == 'workflow_dispatch' ||
-      (github.event_name == 'issue_comment' &&
-       github.event.issue.pull_request != null &&
-       contains(github.event.comment.body, '/links'))
+      contains(github.event.head_commit.message, '/links')
     runs-on: eulernest
     container:
       image: git.eulernest.eu/conformallab/ci-cpp:latest
 
     steps:
       - uses: actions/checkout@v4
-        with:
-          ref: ${{ github.event_name == 'issue_comment' && format('refs/pull/{0}/head', github.event.issue.number) || github.ref }}
 
       # ── Pure-python internal link check (no external network needed) ────
       # We use the same logic that found the 2 broken links before the