PR #18312: actual before/after service and Git proof
Base: 687bd55533; head: target branch plus takeover diff.
Temporary Git repositories on headless Linux, Git 2.43.0; injected generator.

Before: pinned main with regression tests
 FAIL  apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > measures only the PR change using the renamed verified remote's fetch URL
AssertionError: expected 'feature.txt\nlower.txt' to equal 'feature.txt'
 FAIL  apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > refuses generation when the verified remote disappeared despite a usable origin
AssertionError: expected undefined to equal 'Failed'
 Test Files  1 failed (1)
      Tests  2 failed | 15 passed (17)

After: final service suite
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > writes a guide for the reported commit: a short head already fetched 582ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > writes a guide for the reported commit: a short head on its branch 525ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > writes a guide for the reported commit: a short head whose branch moves during … 578ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > writes a guide for the reported commit: a full head served by commit 530ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > writes a guide for the reported commit: a full head on its branch 523ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > writes a guide for the reported commit: a full head only on its pull ref 569ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > writes a guide for the reported commit: a full head only on its merge request r… 613ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > refuses to write a guide for a branch named like the short head 436ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > refuses to write a guide for a tag named like the short head 620ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > refuses to write a guide for a head that is not a commit hash 413ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > refuses to write a guide for a head no source has 392ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > briefs the change against its own base in a checkout it then removes 472ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > measures only the PR change using the renamed verified remote's fetch URL 532ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > refuses generation when the verified remote disappeared despite a usable origin 216ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > refuses to write a guide while the server has review guides off 200ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > keeps a newer run's guide when an older run for the same pull request finishes late 895ms
 ✓ apps/server/src/pullRequest/PullRequestReviewGuideService.test.ts > PullRequestReviewGuideService > refuses a pull request from a repository the project is not a checkout of 252ms
 Test Files  1 passed (1)
      Tests  17 passed (17)

After: relevant Git compatibility smoke
PASS: effective fetch URL agrees with remote -v under insteadOf
PASS: missing cached name cannot be revived by URL rewriting
PASS: included configuration remote resolves
PASS: option-like remote name stays positional after --