fix: add GitHub Actions permissions for PR validation workflow

- Add permissions block to .github/workflows/pr-validation.yml
- Grant contents:read, pull-requests:write, issues:write, actions:read
- Resolves "Resource not accessible by integration" error for github-script action
- Enables automated PR comment functionality for validation results

Fixes GitHub Actions runs:
- https://github.com/minipuft/claude-prompts-mcp/actions/runs/16542308461/job/46785195194
- https://github.com/minipuft/claude-prompts-mcp/actions/runs/16542308459

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: minipuft

.github/workflows/pr-validation.yml

@@ -8,6 +8,12 @@ on:
 env:
   NODE_ENV: test
 
+permissions:
+  contents: read
+  pull-requests: write
+  issues: write
+  actions: read
+
 jobs:
   pr-quality-gates:
     name: Pull Request Quality Gates