The waveform column's vertical extents move to pure component_geometry so the shared
primitive stops being untested; PlaySeconds hoists into a header-only play_seconds target.
Cancels the curve-node drag whenever the popup closes so Esc mid-drag can't alias the amp curve; generalizes CurveTarget routing to one switch; fixes stale/overstated comments; clamps a pre-v12 depth fold; adds deck-inertness and filter-fold test coverage.
Corrects theme.h's large-text thresholds, names accent/secondary's real
binding limiter, and adds compositeOver so the loop-span fill's 2.25:1
under-floor pair is asserted rather than assumed.
daniel