refactor(github): extract CI dispatch decisions

[aaight]

Summary

Refactors the highest-risk GitHub CI dispatch paths into smaller decision and result-building units.

Card: https://trello.com/c/69fe2a760699baaf91682dc3

Changes

• Added shared check-suite PR resolution for direct payload PRs, refs/pull/N/head, and branch lookup fallback.
• Added a pure check-suite decision helper that classifies aggregate check-run state into defer, respond-to-ci, review, or skip while preserving existing skip messages.
• Centralized GitHub PR dispatch result creation for review, respond-to-ci, and resolve-conflicts paths.
• Wired check-suite-success, check-suite-failure, respond-to-ci-dispatch, and pr-conflict-detected through the extracted helpers while keeping GitHub API calls, dedup claims, counters, and comments at handler boundaries.
• Updated the static trigger-event guard to understand the new GitHub result builders.
• Added focused unit tests for aggregate mixed/failing state, incomplete checks, gate skips, and shared PR resolution paths.

Verification

• npx vitest run --project unit-triggers tests/unit/triggers/github/check-suite-decision.test.ts tests/unit/triggers/check-suite-success.test.ts tests/unit/triggers/check-suite-failure.test.ts tests/unit/triggers/pr-conflict-detected.test.ts
• npm test
• npm run typecheck
• npm run lint (passes with existing complexity warnings in src/integrations/alerting/_shared/materialize.ts and src/triggers/sentry/webhook-handler.ts)

🕵️ codex · gpt-5.5 · run details

[codecov]

Codecov Report

❌ Patch coverage is 93.63958% with 18 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/triggers/github/check-suite-decision.ts	86.31%	13 Missing ⚠️
src/triggers/github/check-suite-success.ts	92.00%	4 Missing ⚠️
src/triggers/github/check-suite-failure.ts	97.05%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[nhopeatall]

LGTM - I traced the extracted PR-resolution, check-suite decision, and GitHub result-builder paths against the existing trigger contracts and the linked card requirements. The dispatch payloads preserve triggerEvent/prNumber/workItemId, review onBlocked dedup release remains at the handler boundary, and the targeted unit-trigger suite passed locally.

🕵️ codex · gpt-5.5 · run details