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/shell/instrument/editor_input_chrome.cpp

@@ -7,6 +7,7 @@
 #ifdef _WIN32
 
 #include "core/instrument/ui/keyboard_strip.h"  // keyAtPoint / resolveDragNote (root key)
+#include "core/instrument/ui/knob_deck.h"       // inKnobFace (the shared reset target rule)
 #include "shell/instrument/editor_internal.h"
 #include "shell/instrument/reasampler_processor.h"
 
@@ -82,11 +83,10 @@ bool ReaSamplerEditor::mouseDownChrome(const FaceLayout& fl, int x, int y) {
 
 bool ReaSamplerEditor::doubleClickChrome(const FaceLayout& fl, int x, int y) {
     // The preview-velocity dial answers the same reset gesture the deck's knobs do — it is a
-    // radial knob drawn by the same primitive, so a user who learns the gesture there expects
-    // it here. Resolved against the whole cell, not the circle: the cell IS the knob's target
-    // on this surface (there is no neighbouring control to steal from).
+    // radial knob drawn by the same primitive, so it resolves through the same target rule
+    // (inKnobFace), against the drawn circle rather than the cell's label band.
     if (selectedId_.empty() || !processor_) return false;
-    if (!contains(fl.chrome.velCell, x, y)) return false;
+    if (!inKnobFace(fl.chrome.velKnob, x, y)) return false;
     processor_->setPreviewVelocity(kPreviewVelocityDefault);
     invalidate();
     return true;