Plan: Migrate PhaseHooksService from GitHubService to PlatformProvider#

Summary#

Replace direct GitHubService injection in PhaseHooksService with the PlatformProvider interface (from #345), making phase hooks platform-agnostic. This is a Wave 2 consumer migration in the multi-tenant initiative.

Files#

File	Action	Description
`src/hooks/phase-hooks.service.ts`	modify	Swap `GitHubService` injection for `@Inject(PLATFORM_PROVIDER) PlatformProvider`; replace all `this.github.` calls with `this.platform.`; use optional chaining on `setProjectItemStatus`
`src/hooks/phase-hooks.module.ts`	modify	Replace `GitHubModule` import with `PlatformModule`
`src/hooks/phase-hooks.service.spec.ts`	modify	Replace `GitHubService` mock with `PLATFORM_PROVIDER` token mock using the `PlatformProvider` interface type

Steps#

Update phase-hooks.service.ts constructor injection — Replace private readonly github: GitHubService with @Inject(PLATFORM_PROVIDER) private readonly platform: PlatformProvider. Remove GitHubService import, add PlatformProvider and PLATFORM_PROVIDER imports from the platform module.
Replace all this.github.* call sites — Rename every this.github.addLabel, removeLabel, postComment, mergePR, closePR, closeIssue, getCheckStatus, getReviewStatus to this.platform.*. Change this.github.setProjectItemStatus(...) to this.platform.setProjectItemStatus?.(...) with optional chaining.
Update phase-hooks.module.ts — Replace GitHubModule import with PlatformModule. Remove GitHubModule import statement.
Update phase-hooks.service.spec.ts — Change the mock provider from { provide: GitHubService, useValue: {...} } to { provide: PLATFORM_PROVIDER, useValue: {...} }. Update the mock retrieval from module.get(GitHubService) to module.get(PLATFORM_PROVIDER). Update the type annotation from jest.Mocked<GitHubService> to jest.Mocked<PlatformProvider>.

Verification#

tsc --noEmit passes with no errors
npm run lint passes with zero warnings
npm run test -- --testPathPattern=phase-hooks — all existing tests pass with PlatformProvider mock

Risks#

Blocked by #345: PlatformProvider interface and PlatformModule must land on rc/multi-tenant first. Do not merge this PR until #345 is merged.
setProjectItemStatus optional chaining: If PlatformProvider types setProjectItemStatus as required (not optional), the ?. syntax may need adjustment to match the interface definition.