Two pre-existing failures the segfault had been masking (the run aborted at ~25%, so they never ran until #735 let the suite complete):
1) Tuner group (~24): plugins ship a bare-named routes.py, so sys.modules['routes'] leaked between plugin test dirs (achievements ran first, tuner got its module). Each plugin conftest now pops the stale 'routes' and an autouse fixture binds sys.modules['routes'] to that plugin's module for the duration of its tests (covers runtime 'import routes' in test bodies).
2) Diagnostics group (5): _SONG_FILENAME_RE never matched the tests' .feedpak/.archive filenames — it also lacked 'feedpak' (the current primary format), a real redaction gap. Added feedpak to the regex and switched the tests off the fake .archive to the real .feedpak. Verified: full suite 2183 passed, 0 failed.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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