test: smoke-test the test-modification detector (do not merge)

[RagingRedRiot]

Throwaway PR to exercise the detect-test-modifications job from PR #3. The change is a single comment line in tests/promote.rs. Will be closed without merging once the detector is verified.

[RagingRedRiot]

Smoke test results

This PR exercised the detect-test-modifications job from #3 without merging. Two workflow runs cover both the post and delete paths:

Step	Commit	Workflow run	Result
Modify an existing test (single comment line in tests/promote.rs)	e67594a	26424416734	Detector posted a PR comment listing tests/promote.rs (1 line(s) removed or changed); job summary recorded the ⚠️ warning. fmt / clippy / test all green.
Revert the modification	74090ed	26424541430	Detector found the existing marker comment and deleted it (the original warning comment is no longer present on this PR); job summary recorded ✅ "No existing tests were modified". fmt / clippy / test all green.

Both paths verified. Closing without merging.

[RagingRedRiot]

Smoke test complete — see the evidence comment above. Closing without merging; the modification was deliberate test fodder for the detector and is not intended to land.