audio_lens.py consolidates the spectral toolbox (profile / stemmap / mix) so the
machine catches OBJECTIVE audio defects autonomously, reserving PLN's ears for
subjective feel.

- profile(file): band-energy % + centroid → is_broadband() gate (centroid >140Hz
  and >18% energy above 150Hz). A pure-kick mix is centroid ~111Hz, mid<12% → FAIL.
- mix(take, --orbits): EXPLICIT numpy sum of local interchange stems (no amix black
  box, no freebox), peak-normalized, then SELF-VERIFIES the render is broadband and
  exits non-zero on FAIL. Caught + fixed the kick-clone bug that shipped twice.
- stemmap(take): per-orbit activity (driving/sparse/silent) for arrangement reads.

Take35 mix rebuilt via the tool (v3): cen 168Hz, mid present, PASS — replaces the
two broken kick-clone mixes (deleted). Lesson: measure your own output; extend the
toolbox, no /tmp throwaways.

EDL: seed_edl_take89.py + master_edl_take89.json (9 typed edits, 3 bad_cut labels)
from PLN's WH-1000XM5 review, logged in performance_notes.md. tasks/011 captures the
TF-IDF + verify-your-output story. #25 reframed: auto-detect boundary sample-leak.