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/cpp-tests.yml

@@ -1,5 +1,14 @@
 name: C++ Tests
 
+# Trigger keywords in commit message (checked via head_commit.message):
+#   /test-cgal      — full CGAL test suite (277 tests, ~5 min build)
+#   /quality-gates  — license, codespell, shellcheck, CGAL conventions
+#
+# Example commit:
+#   git commit -m "fix: correct angle formula /test-cgal"
+#
+# test-fast always runs on every push — it is fast (< 5 s) and cheap.
+
 on:
   push:
     branches:
@@ -7,15 +16,13 @@ on:
       - dev
       - "claude/**"
       - "feature/**"
+      - "review/**"
   pull_request:
-  # /test-cgal comment on any PR triggers the CGAL test suite manually.
-  issue_comment:
-    types: [created]
 
 # ─────────────────────────────────────────────────────────────────────────────
 # Job 1 — test-fast
 #   Pure-math tests (Clausen, ImLi₂, Hyper-ideal geometry).
-#   No CGAL, no Boost. Eigen + GTest only. Runs on ALL branches.
+#   No CGAL, no Boost. Eigen + GTest only. Runs on EVERY push.
 # ─────────────────────────────────────────────────────────────────────────────
 jobs:
   test-fast:
@@ -51,59 +58,32 @@ jobs:
 
 # ─────────────────────────────────────────────────────────────────────────────
 # Job 2 — test-cgal
-#   Full CGAL test suite (Phase 3–7, 158 tests).
-#   Runs ONLY on pull requests (not on direct pushes to dev/main).
-#   Starts only after test-fast succeeds.
 #
-#   Uses -DWITH_CGAL_TESTS=ON (not -DWITH_CGAL=ON) to avoid building
-#   Viewer/GLFW — the CI container has no wayland-scanner.
+# Trigger: include "/test-cgal" anywhere in the commit message.
 #
-#   Boost (libboost-dev) is already present in the container since the image rebuild.
+#   git commit -m "fix: correct angle formula /test-cgal"
+#
+# Why keyword-triggered (not automatic on every push):
+#   The Pi runner (3-4 GB RAM, swap heavily loaded) cannot sustain a
+#   CGAL build on every WIP commit.  Adding the keyword to a commit
+#   message explicitly signals "this commit is ready for full testing".
+#
+# LOW_MEMORY_BUILD applies four RAM-saving measures so the build fits in
+# a 2000 MB container: -O0, no PCH, unity batch 1, --no-keep-memory.
+# See code/tests/cgal/CMakeLists.txt for the full explanation.
 # ─────────────────────────────────────────────────────────────────────────────
-  # ─── CGAL tests: manual trigger via PR comment ───────────────────────────
-  #
-  # Trigger: write "/test-cgal" as a comment on any pull request.
-  #
-  # Why comment-triggered (not automatic on every PR push):
-  #   The Pi runner has 3-4 GB RAM total with swap constantly loaded.
-  #   Even with LOW_MEMORY_BUILD the CGAL build takes ~5 min and stresses
-  #   the runner.  Triggering on every push would queue builds faster than
-  #   the Pi can drain them.  A manual trigger gives full control: run the
-  #   277-test suite when a PR is ready for review, not on every WIP commit.
-  #
-  # How it works:
-  #   - `issue_comment` fires on all PR + issue comments.
-  #   - The `if:` condition checks:
-  #       1. Event is a comment (not a push or PR sync)
-  #       2. The comment is on a PR (issue.pull_request != null)
-  #       3. The comment body contains "/test-cgal"
-  #   - The checkout uses refs/pull/N/head to get the PR branch, because
-  #     `issue_comment` does not set GITHUB_REF to the PR branch by default.
-  #
-  # LOW_MEMORY_BUILD applies four RAM-saving measures so the build fits in
-  # 2000 MB: -O0, PCH off, unity batch 1, --no-keep-memory linker.
-  # See code/tests/cgal/CMakeLists.txt for the full explanation.
   test-cgal:
     needs: test-fast
-    if: |
-      github.event_name == 'issue_comment' &&
-      github.event.issue.pull_request != null &&
-      contains(github.event.comment.body, '/test-cgal')
+    if: contains(github.event.head_commit.message, '/test-cgal')
     runs-on: eulernest
     container:
       image: git.eulernest.eu/conformallab/ci-cpp:latest
       # 2000 MB hard limit; 1000 MB swap headroom (memory-swap = RAM + swap).
-      # Uses ~half of the Pi's 3-4 GB, leaving margin for OS + runner daemon.
       # With LOW_MEMORY_BUILD peak per TU is ~150-200 MB → well within limit.
       options: "--memory=2000m --memory-swap=3000m"
 
     steps:
-      # Check out the PR branch, not the default branch.
-      # issue_comment events set GITHUB_REF to the default branch; we need
-      # refs/pull/N/head to get the actual PR code.
       - uses: actions/checkout@v4
-        with:
-          ref: refs/pull/${{ github.event.issue.number }}/head
 
       - name: Configure (LOW_MEMORY_BUILD — -O0, no PCH, unity batch 1)
         run: |
@@ -133,44 +113,29 @@ jobs:
             echo "CGAL  ▸ TOTAL ${total:-0} | PASSED $passed | FAILED ${failed:-0} | SKIPPED ${skipped:-0}"
           fi
 
-      # ── Structural gate: doc/api/tests.md totals match ctest reality ───
-      # Single source of truth for test counts (see doc/release-policy.md).
-      # Reuses the already-built ./build dir via BUILD_DIR env var, so this
-      # adds ~5 s on top of the existing CGAL job.
       - name: Verify test-count consistency (doc/api/tests.md)
         run: BUILD_DIR=build bash scripts/check-test-counts.sh
 
-      # ── Structural gate: end-to-end smoke (try_it.sh) ──────────────────
-      # The user-facing quick-start script: configure + build + run the
-      # full ctest + run the Euclidean example on a bundled mesh.  If
-      # this regresses, README quick-start instructions are broken.
-      # try_it.sh creates its own build-try/ — accept the ~3 min cost as
-      # the price of guaranteeing the documented workflow stays working.
       - name: End-to-end smoke test (scripts/try_it.sh)
         run: bash scripts/try_it.sh
 
 # ─────────────────────────────────────────────────────────────────────────────
-# Job 3 — quality-gates  (style + convention block)
+# Job 3 — quality-gates
 #
-# Trigger: write "/quality-gates" as a comment on any pull request.
+# Trigger: include "/quality-gates" anywhere in the commit message.
 #
-# Cheap, deterministic checks (~30 s): license headers, CGAL conventions,
-# codespell, shellcheck.  Runs independently of test-fast when comment-
-# triggered (no `needs:` — the caller decides when to invoke it).
+#   git commit -m "chore: update docs /quality-gates"
+#
+# Cheap (~30 s): license headers, CGAL conventions, codespell, shellcheck.
 # ─────────────────────────────────────────────────────────────────────────────
   quality-gates:
-    if: |
-      github.event_name == 'issue_comment' &&
-      github.event.issue.pull_request != null &&
-      contains(github.event.comment.body, '/quality-gates')
+    if: contains(github.event.head_commit.message, '/quality-gates')
     runs-on: eulernest
     container:
       image: git.eulernest.eu/conformallab/ci-cpp:latest
 
     steps:
       - uses: actions/checkout@v4
-        with:
-          ref: refs/pull/${{ github.event.issue.number }}/head
 
       - name: Install codespell + shellcheck (job-local)
         run: |