Adds a hairline outline for Disabled chrome buttons, resolves Hover on the four
mode-selector single-buttons, re-measures the control-surface doc's 1.2 layout
table post-reflow, and adds a structural test pinning every enable/mode toggle
to a derived segment.
Swap nearbyint for std::round (MXCSR-independent); derive the finest-drag test
from the editor floor, not the knob; verify resets against fields, not norms;
record the spline-point modifier exclusion.
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.
daniel