ci(placement-guard): set job timeout-minutes

Addresses the Hypatia workflow-audit "missing_timeout_minutes" finding for
the new workflow so this PR does not introduce a newly-flagged file.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W8DXRHQRBgxwSdDz8om287

Author: claude

.github/workflows/placement-guard.yml

@@ -20,6 +20,7 @@ jobs:
   placement:
     name: Content placement check
     runs-on: ubuntu-latest
+    timeout-minutes: 10
 
     steps:
       - name: Checkout repository