Stop flagging tonal one-shots as percussive

Commit notes

analyze_classification's catch-all marked any short, fast-attack sound is_percussive=True even with no drum_type — but a pitched pluck, synth stab, or 808 is also short and fast-attack. That false percussive flag then forced the key-reliability rules to demand overwhelming (0.9/0.45) evidence, stripping the detected key off legitimately tonal one-shots.

The catch-all now requires actual inharmonic evidence (no tonal hint and percussive-dominant HPSS energy) before calling an unclassified sound percussive. The decision lives in the pure, unit-tested classification_rules module alongside the key gating.

[private session redacted]