fix(ci): restore issues:write for gh pr comment in pr-overview.yml

The app token in pr-overview.yml runs `gh pr comment`, which posts via the
GitHub Issues API endpoint and requires `issues: write`. The hardening pass
dropped this scope from both the top-level permissions and the app token,
which would cause the overview comment to fail with a 403.

Restore `issues: write` to match the working claude-review.yml pattern.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: emptyhammond

.github/workflows/pr-overview.yml

@@ -7,6 +7,7 @@ on:
 permissions:
   contents: read
   pull-requests: write
+  issues: write
 
 jobs:
   generate-overview:
@@ -32,7 +33,8 @@ jobs:
           private-key: ${{ secrets.CLAUDE_APP_PRIVATE_KEY }}
           permissions: >-
             contents:read,
-            pull-requests:write
+            pull-requests:write,
+            issues:write
 
       - name: Generate PR Overview
         uses: anthropics/claude-code-action@1dc994ee7a008f0ecc866d9ac23ef036b7229f84 # v1