chore: protect workflow files from fork merge deletions

Add .gitattributes with merge=ours strategy for:
- Claude review workflow
- Template cleanup workflow
- Claude PR review script

This prevents these files from being deleted when merging PRs
from forks that have run the cleanup workflow.

Author: eyaprak

.gitattributes

@@ -0,0 +1,5 @@
+# Protect workflow files from being deleted during merges from forks
+# These files should always be preserved in the main repository
+.github/workflows/claude-review.yml merge=ours
+.github/workflows/template-cleanup.yml merge=ours
+scripts/claude-pr-review.ts merge=ours