fix(draw_kit): reclaim 4x waveform oversample; relocate waveformColumnCount to component_geometry

kWaveformOversample set to 1 (was 4) — overbinning produced byte-identical pixels because columnMinMax exact partition already makes the draw gap-free. Comments credit columnMinMax, not oversampling.

src/component_geometry.h

@@ -126,4 +126,14 @@ ListRowBox computeListRow(const KitBox& list, int index, int rowHeight);
 // a phantom row. Half-open bounds match computeListRow so the hit maps to the drawn row.
 int hitTestListRow(int px, int py, const KitBox& list, int rowHeight, int rowCount);
 
+// --- Waveform column count ---------------------------------------------------
+//
+// The number of pixel columns drawWaveform renders inside `box` (its fixed 2px side
+// insets), never negative. Callers pass this count directly as the `binCount` argument to
+// peaks::computeEnvelope — one bin per column is the correct resolution, and
+// peaks::columnMinMax's exact partition makes the render gap-free at any bins-to-pixels
+// ratio. Overbinning does NOT improve render quality (columnMinMax's frame union is
+// identical whether bins == columns or bins == k*columns) and wastes memory and CPU.
+int waveformColumnCount(const KitBox& box);
+
 } // namespace reasampler