fix: update webhook fixtures with real payload data

[xmtp-coder-agent]

Resolves #66

Summary

• Replaced all 9 minimal webhook fixture files with real GitHub webhook payloads from production
• Updated test assertions in webhook-router.test.ts, webhook-schemas.test.ts, and integration.test.ts to match the real payload values
• Fixtures that had no exact real payload match (e.g., workflow-run-failure, pr-review-submitted with body, issue-comment-on-pr) were derived from real payloads with minimal modifications

Key changes

• Fixture data: Real payloads from xmtplabs/coder-action repo (installation ID 118770088, repo owner xmtplabs, human user neekolas)
• App bot login: Updated from xmtp-coder-app[bot] to xmtp-coder-tasks[bot] to match real app identity
• All 181 tests pass with full check suite (typecheck + lint + format + tests)

Test plan

• bun run check passes (typecheck + lint + format:check + test)
• All 181 tests pass across 18 files
• Zod schema validation works with real payload structure (passthrough handles extra fields)

Note

Update webhook test fixtures with real GitHub API payload data

Replaces minimal placeholder fixtures in src/__fixtures__/ with complete GitHub API payloads sourced from real events in the xmtplabs/coder-action repository. Updates all corresponding test expectations in webhook-schemas.test.ts, webhook-router.test.ts, and integration.test.ts to match the new IDs, repository coordinates, and user logins present in the updated fixtures.

^{Macroscope summarized 1950c03.}