ci: add PR title prefix enforcement

.coderabbit.yaml

@@ -0,0 +1,12 @@
+# yaml-language-server: $schema=https://coderabbit.ai/integrations/schema.v2.json
+reviews:
+  request_changes_workflow: true
+  path_instructions:
+    - path: "**"
+      instructions: |
+        Check whether the PR title prefix allowed in the pr-title.yml workflow
+        accurately describes the changes. Flag e.g. if a PR labeled "fix" appears to add
+        new functionality, if a "feat" PR only refactors existing code, or if a
+        "chore" PR contains logic changes that should be a "feat" or "fix".
+        If a PR mixes unrelated concerns (e.g., a bug fix bundled with a refactor
+        or new feature), suggest splitting it into separate focused PRs.

.github/workflows/pr-title.yml

@@ -0,0 +1,30 @@
+name: PR Title Check
+
+on:
+  pull_request_target:
+    types: [opened, edited, synchronize]
+
+permissions:
+  pull-requests: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  check-title:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: amannn/action-semantic-pull-request@v6
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          types: |
+            build
+            chore
+            ci
+            docs
+            feat
+            fix
+            refactor
+            test