fix(github): honor the saved project account for PR requests (#35023)

* fix(github): resolve project accounts at the request boundary

* fix(github): retain account identity through request settlement

* fix: isolate GitHub leaf caches by held execution identity

* fix: use canonical options type for merged review membership

src/main/github/github-pr-stack.test.ts

@@ -94,7 +94,7 @@ describe('hydrateGitHubPRStack', () => {
       repository,
       201,
       { ...summary, position: 1 },
-      { cwd: '/other-worktree' }
+      { cwd: '/repo' }
     )
 
     expect(first).toMatchObject({