[metoocrib-lang]

Saving a Provider Hub candidate explicitly marked as verifiable non-HI can
change its destination from episode.es.srt to episode.es.hi.srt when ordinary
dialogue contains parentheses. This may also target an existing HI file.

Honor hearing_impaired_verifiable is True together with
_reported_hearing_impaired is False before applying the content heuristic.
This applies to any provider carrying those facts. Missing, unverified or
malformed metadata retains the heuristic; existing HI language flags and
explicit remove_HI behavior remain unchanged.

The regression test runs the actual saver and regex functions extracted from
its AST, with in-memory destinations. Register it in the Backend suites CI
step so the test is collected on future pull requests.

Validation

Base: development, commit effe5a9cc6e21910ab659ab41e0481479aa5b5f0.

• Python 3.13 on Windows: four regression tests, eleven scenarios pass.
• Running those tests against the unchanged development saver produces exactly
  the two expected failures for verified normal subtitles; the other nine
  scenarios pass.
• Ruff passes for the added test. The upstream Ruff configuration excludes
  custom_libs; git diff --check also passes.
• Isolated pytest run (--noconftest) of the regression and CI guard:
  236 passed, 7 failed. The failures concern one omitted sparse-checkout file,
  Windows symbolic-link privileges, and five PostgreSQL guard subprocesses
  missing SQLAlchemy in the minimal environment. The new test registration
  passes the guard. This is not a passing full CI run.
• Full application CI and the PostgreSQL runner have not been run. No running
  services or library files were changed. Please keep this proposal in draft
  until full CI has completed successfully.