Silence the three autonerves-rooted CLI-noise sources

[Jammy2211]

Implements PyAutoMind draft/maintenance/pyautonerves/cli_noise_autonerves_batch.md — the three CLI-noise root causes from the 2026-08-06 /cli_noise_clean audit:

1. fits leak — ndarray_via_fits_from called fits.open without closing, emitting ResourceWarning: unclosed file in every downstream repo that loads FITS. Now uses with fits.open(...); the same fix is applied to header_obj_from, which had the identical unclosed-handle pattern.
2. pytest collection — test_test_mode.py imported the real API functions test_mode_level/test_mode_samples by bare name, so pytest collected them as tests (PytestReturnNotNoneWarning, an ERROR in a future pytest). The unused test_mode_level import is dropped and test_mode_samples is aliased to _test_mode_samples with a comment explaining why.
3. check_version false positive — with workspace_root defaulting to cwd, every library import from inside a library's own source repo warned "Cannot verify the workspace ... is compatible". check_version now skips silently when the root is a package source checkout (setup.py or pyproject.toml at its top level) and no version floor is recorded. A recorded floor is still enforced, and a genuine workspace missing its version keys still warns.

Surface decision noted in the Mind prompt: check_version remains the surface of the workspace-facing libraries (autofit/autogalaxy/autolens); autoarray/autonerves intentionally do not call it.

Regression tests added for all three; full test_autonerves suite passes 157/157 under pytest -W all with none of the three warnings remaining.

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https://claude.ai/code/session_015NrwGppUCg8r4Foed6bgSf

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