ci: add PR title check for conventional commits

Add GitHub workflow that validates PR titles follow conventional commit
format since we squash PRs and use the title as the commit message.

The check validates:
- PR title follows format: type(scope)?: description
- Allowed types: feat, fix, chore, docs, style, refactor, perf, test,
  build, ci, revert, deps
- Breaking changes can be indicated with '!' (e.g., feat!: breaking change)
- Subject should start with lowercase
- Scope is optional

This ensures consistent commit history and proper semantic versioning
when PRs are squashed and merged.

Author: eablack

.github/workflows/pr-title-check.yml

@@ -0,0 +1,47 @@
+name: PR Title Check
+
+on:
+  pull_request:
+    types: [opened, edited, synchronize, reopened]
+
+jobs:
+  check-pr-title:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check PR title follows Conventional Commits
+        uses: amannn/action-semantic-pull-request@v5
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          # Configure which types are allowed
+          types: |
+            feat
+            fix
+            chore
+            docs
+            style
+            refactor
+            perf
+            test
+            build
+            ci
+            revert
+            deps
+          # Require a scope (optional - set to false if scope is not required)
+          requireScope: false
+          # Configure which scopes are allowed (optional)
+          # scopes: |
+          #   core
+          #   api
+          #   cli
+          # If the PR title should have a subject (default: true)
+          subjectPattern: ^(?![A-Z]).+$
+          subjectPatternError: |
+            The subject "{subject}" found in the pull request title "{title}"
+            didn't match the configured pattern. Please ensure that the subject
+            doesn't start with an uppercase character.
+          # Validate the entire PR title against a regex
+          # This ensures format is: type(scope)?: description
+          # Or with breaking change: type(scope)!: description
+          headerPattern: '^(\w+)(\(\w+\))?!?: .+$'
+          headerPatternCorrespondence: type, scope, subject