fix: add missing permissions block to claude-cross-repo job

The claude-code-action needs id-token: write to fetch an OIDC token.
The claude-cross-repo job was missing its permissions block entirely,
causing it to fail with "Could not fetch an OIDC token".

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.github/workflows/claude.yml

@@ -72,6 +72,11 @@ jobs:
     if: github.event_name == 'repository_dispatch'
     runs-on: ubuntu-latest
     timeout-minutes: 60
+    permissions:
+      contents: write
+      pull-requests: write
+      issues: write
+      id-token: write
     services:
       postgres:
         image: postgres:16