refactor: remove dead quarantine state helper

[promiseeuler]

Summary

While reviewing the catalog implementation for issue #64, I found that latest_quarantine_state() is a private wrapper with no callers, exports, tests, or documentation. This removes that dead helper and changes nothing else.

Closes #64

Why

The richer latest_quarantine() result is already used by the real consumer. Keeping the unused wrapper adds an extra maintenance surface without providing an API or behavior.

Validation

• rg -n "latest_quarantine_state" src tests docs examples README.md — no matches after the change
• uv run ruff check — passed
• uv run ruff format --check — passed (97 files already formatted)
• uv run ty check — passed
• uv run pytest -q — 391 passed, 6 skipped; 7 environment-dependent failures unrelated to this deletion (this macOS environment lacks /usr/bin/ffmpeg, Python lzma, and FFmpeg's drawtext filter)
• git diff --check — passed

Checklist

• No business logic changed, so no outcome-focused test is needed.
• No behavior, flag, format, or requirement changed, so documentation is unchanged.
• I ran Ruff formatting/lint and ty check.
• I ran the relevant pytest suite and documented its environment-only failures above.
• I did not add recordings, generated media, credentials, private URLs, or runtime artifacts.
• Stored-data compatibility is unchanged.

[github-actions]

👋 Hi @promiseeuler — thanks for the contribution! To keep starter issues available
for other contributors and give every pull request a real review, we accept
1 open pull request per contributor at a time.

You already have #106 open, so this one is being closed automatically.
Once your open pull request is merged or closed, feel free to reopen this one —
no work is lost.

[promiseeuler]

Thanks for the guidance. #106 is now merged, but GitHub is not exposing a Reopen pull request control to me on this page (I only have the comment composer). Could you reopen #107 when convenient? The branch and commit are intact, and the existing 5/5 checks passed.

[promiseeuler]

Correction to my previous note: please leave #107 closed for now. I subsequently opened #112, and HFlow accepts one open pull request per contributor. I’ll revisit #107 only after #112 is resolved so the queue stays within the project’s contribution policy.

[promiseeuler]

Thanks — I rechecked #107 before reopening it. Its exact commit a0388a7 no longer applies cleanly to current main at 2f99071: merged PR #116 (87154c1) replaced the surrounding LatestQuarantine / latest_quarantine API with QuarantineHistory and latest_quarantine_tags, removing latest_quarantine_state in the process.

On current main, git grep latest_quarantine_state returns no matches, and replaying a0388a7 conflicts at that already-replaced block. The cleanup this PR intended is therefore already present, so I’m leaving #107 closed rather than reopening obsolete work.