Make the Narrowed-Scan Diff-Floor Test Independent of the Working Directory #2830

Defect

tests/test_prose_lint.py TestDiffScopeFloor.test_a_deliberately_narrowed_scan_is_not_told_the_narrowing_is_a_defect passes only when the test process's working directory contains an entry named catalog.

The test narrows the scan with the bare relative path catalog, and it mocks repo_root, discover, and changed_lines. It never creates catalog under its temporary root. Before the diff-floor logic runs, prose_lint.main refuses any requested path that is neither a file nor a directory relative to the working directory, and returns 2. The hub's root happens to have a tracked catalog/ directory, so a run from the root passes and a run from anywhere else fails with 0 != 2. The floor logic under test is not at fault.

Repro

From a clean develop checkout:

• cd tests && python3 -m unittest test_prose_lint.TestDiffScopeFloor.test_a_deliberately_narrowed_scan_is_not_told_the_narrowing_is_a_defect fails with AssertionError: 0 != 2.
• python3 -m unittest discover -s tests -p test_prose_lint.py -k narrowed, run from the root, passes.

CI and the file's own header both run from the root, so CI stays green, and the defect shows up only in a local run started elsewhere.

Proposed fix

Make the test self-contained: create self.tmp / "catalog" and pass str(self.tmp / "catalog") as the narrowing argument, so the path resolves against the mocked root rather than the working directory. Check the sibling tests that pass a relative path for the same dependence.