Task 3.1: End-to-end GitHub App integration testing

[ajianaz]

Task: E2E GitHub App Testing

Test the full GitHub App flow after backend is deployed.

Test Cases

• Install GitHub App on test repo
• Open test PR → webhook received by backend
• PR comment posted with review findings
• Check run created with pass/fail status
• BYOK works: API key from .cora.yaml in repo
• Timeout handling: large PR does not hang
• Error handling: invalid API key → helpful error message
• Empty diff → "No files to review" comment
• Binary-only PR → "No reviewable files" comment
• Very large PR (100+ files) → graceful handling
• PR from fork → permissions work correctly

Expected Output Per Test

• PR comment with structured findings (file, line, severity, title, body)
• Check run: "Cora Review" — success if no critical/major, failure if issues found
• Response time < 60s for small/medium PRs

Part Of: #118, #121
Depends On: #132 (GitHub App backend MVP)