Add test fixture for partial doc deletion in a folder

[csoceanu]

The regression that motivated #76 — partial deletion inside a folder that still has files — is fixed by the entrypoint fetch, but the code path itself has no test coverage in the test suite.

This is awkward to unit-test since it depends on git ref state. The right home is an integration fixture in the eval harness (#65). The fixture should:

• Set up a repo with a docs subfolder containing multiple files in a folder
• Delete some (not all) files from the folder on the base branch
• Run [review-docs] against a stale origin/main
• Verify the action correctly identifies remaining docs need updating

Follow-up from #76.

[fullsend-ai-triage]

🤖 Finished Triage · ✅ Success · Started 12:13 PM UTC · Completed 12:16 PM UTC

Commit: 9f4552c · View workflow run →

[fullsend-ai-triage]

This issue is blocked on PR #65 — the fixture-based evaluation harness. The issue explicitly identifies the eval harness as the right home for this integration test, and that PR introduces the runner, case folder structure, and assertion framework that the partial-deletion fixture would use.

Once the eval harness merges, this issue is well-scoped and ready to implement: the fixture should set up a repo with a docs subfolder, delete some (not all) files from a folder on the base branch, run [review-docs] against a stale origin/main, and verify remaining docs are correctly identified for updating.

Blocked by:

• feat: fixture-based evaluation harness #65