fix: restore waveform symmetry about the midline, cut deck_values' link to the bank model, and unit-test the column arithmetic

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.

src/core/instrument/ui/knob_deck.h

@@ -153,11 +153,18 @@ struct DeckFaceHit {
     bool inner = false;  // inside the concentric inner disc
 };
 
+// A point inside the circle inscribed in `knob`, boundary-EXCLUSIVE. THE target rule for the
+// reset gesture wherever a radial knob is drawn — the deck's own faces and the chrome's
+// preview-velocity dial both resolve through it, so one gesture cannot grow two target rules.
+bool inKnobFace(const Rect& knob, int x, int y);
+
 // Resolved against the drawn CIRCLES, not the cell: a reset is aimed at a dial, so the label
-// band and the cell margins must miss where a drag grab deliberately does not. Both radii are
-// boundary-EXCLUSIVE, one rule for both rings — a point exactly on the inner radius is an
-// outer-ring hit, one exactly on the outer radius is a miss. Whether a cell actually carries an
-// inner value is deck_groups' call, exactly as with DeckHit::inner.
+// band and the cell margins must miss where a drag grab deliberately does not. One rule for
+// both rings — a point exactly on the inner radius is an outer-ring hit, one exactly on the
+// outer radius is a miss. Whether a cell actually carries an inner value is deck_groups' call,
+// exactly as with DeckHit::inner. Unlike hitTestDeck this runs NO toggle/radio precedence pass
+// first, which is only correct while no toggle rect overlaps a knob circle — a layout change
+// that lets them overlap has to give this the same precedence order.
 DeckFaceHit hitTestKnobFace(const DeckLayout& layout, int x, int y);
 
 }  // namespace reasampler::instrument::ui