fix(ci): support squash merge format in notify workflow (#491)

The workflow was only looking for 'Merge pull request #123' format,
which is used for regular merges. When using 'gh pr merge --squash',
GitHub creates a squash commit with format 'Title (#123)' instead.

**Changes:**
- Updated regex to match BOTH formats:
  - Regular merge: "Merge pull request #123 from..."
  - Squash merge: "Title (#123)"
- Use head -1 to only check first line of commit message

**Testing:**
- Tested regex with both formats
- Regular merge: ✓ Extracts 123
- Squash merge: ✓ Extracts 485

This fixes the workflow not triggering on PR #485 merge.

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: julienld

.github/workflows/notify-dev-channel.yml

@@ -29,12 +29,13 @@ jobs:
           COMMIT_MSG=$(git log -1 --pretty=%B)
           echo "Commit message: $COMMIT_MSG"
 
-          # Extract PR number from merge commit
+          # Extract PR number from commit message
           # GitHub merge commits have format: "Merge pull request #123 from user/branch"
-          PR_NUM=$(echo "$COMMIT_MSG" | grep -oP 'Merge pull request #\K\d+' || echo "")
+          # GitHub squash merges have format: "Title with (#123)" in first line
+          PR_NUM=$(echo "$COMMIT_MSG" | head -1 | grep -oP '(?:Merge pull request #|[[(]#)\K\d+' || echo "")
 
           if [ -z "$PR_NUM" ]; then
-            echo "No PR number found in merge commit. Skipping notification."
+            echo "No PR number found in commit message. Skipping notification."
             echo "skip=true" >> $GITHUB_OUTPUT
             exit 0
           fi