analyze: load the bundled detector metrics file

[immu4989]

Closes #2003.

DetectorMetrics._load_metrics never found the bundled metrics file, so get_detector_se_sp returned the (1.0, 1.0) fallback for every detector and ci_calculator computed intervals as if each detector were perfect. The failure was only logged at debug level.

Two things were wrong, and the name alone is not sufficient:

• garak.data.path is a LocalDataPath that searches the data dir then the package dir on each /. Wrapping it in Path(...) pinned the lookup to the data dir, where nothing ships.
• The directory was spelled detectors_eval; the data ships as detectors-eval, which is also what _plugins.py and docs/source/detector_metrics.rst use.

Resolving through LocalDataPath also means a genuinely missing resource raises GarakException rather than surfacing as FileNotFoundError, so that is caught to keep the existing graceful fallback.

Verification

• Run the tests and ensure they pass python -m pytest tests/analyze/

  160 passed.

• Verify the thing does what it should

  Two tests added to tests/analyze/test_detector_metrics.py. Before this change both fail; after it, metrics_loaded is True and dan.DAN reports its measured Se 1.0 / Sp 0.75 instead of the fallback.

• Verify the thing does not do what it should not

  A detector absent from the file still returns (1.0, 1.0), and a missing file still degrades gracefully rather than raising.

• Supporting configuration such as a generator configuration file

  Not applicable.

• garak -t <target_type> -n <model_name>

  Not applicable; the change is in report analysis and is covered by unit tests.

[jmartin-tech]

The project file name conventions actually prefer _ to - in directory names to align with the python file structure. This should rename the directory to be more consistent for with other file paths.

I would also hazard that the try block is not necessary to the fix as removing the extra Path() object should be enough for a valid install and enable a user provided override. Though I can see leaving it as an extra guard.

[immu4989]

Thanks, both points taken.

Renamed the directory to detectors_eval rather than changing the loader. You are right on the convention: it was the only hyphenated directory under garak/data, against adaptive_attacks, agent_breaker and sysprompt_extraction. _plugins.py and docs/source/detector_metrics.rst move with it, so the directory, both code references and the doc now agree.

On the guard, I kept it, and probes/audio.py is the precedent I was going from:

try:
    audio_achilles_data_dir = data_path / "audio_achilles"
except GarakException:
    ...

LocalDataPath raises GarakException for an absent resource rather than yielding a path that later fails to open, and _load_metrics is called from __init__, so without a catch a missing file would turn graceful degradation into a constructor raise, and change the behaviour test_instantiate_missing_file describes. Happy to drop it if you would still rather have the simpler form.