catalog.py: remove the dead `latest_quarantine_state()` helper (zero callers)

[kstonekuan]

latest_quarantine_state() has no callers. Removing it is a small, provable
cleanup.

Current behavior

src/hflow/catalog.py:207-216 defines latest_quarantine_state, a thin
bool | None wrapper over latest_quarantine.

A repository-wide search finds only the definition:

rg -n "latest_quarantine_state" src tests docs examples README.md

The helper is not exported from hflow.__init__, has no test, and appears in no
documentation. The real consumer at src/hflow/app.py:1119-1123 uses the richer
latest_quarantine result directly.

Pattern to copy

No replacement is needed. Delete the unused function and use the search above
to confirm that nothing references it.

Definition of done

• latest_quarantine_state no longer exists in the repository.
• No other behavior changes.

Validation

uv sync --locked --all-extras
uv run ruff check --fix
uv run ruff format
uv run ty check
uv run pytest -q

[WilliamK112]

I’d like to take this. I’ll keep the change scoped to removing the unused latest_quarantine_state() helper, confirm there are no remaining references, and run the repository’s lint, type-check, and test commands.

[WilliamK112]

Update after checking the latest main: this cleanup has already landed as part of #116 (commit 87154c1). That change removed latest_quarantine_state(), and a repository-wide search now finds no remaining definition or reference. There is no meaningful diff left for a PR, so this issue can be closed as already resolved.

[kstonekuan]

Closing: you are right, and thank you for checking main before writing the patch. 87154c1 (#116) removed latest_quarantine_state, and it appears nowhere in src/, packages/, tests/, or docs/ today. The issue outlived its defect and nobody noticed.

Checking first is the more useful contribution here, so it is not wasted effort. #66 is yours.