Ctrl held before mouse-down forced the node/toggle win over a smaller cap or
column regardless of area; now it defers to the ordinary smallest-area
arbitration like a plain click. Also amends product docs, VERIFICATION.md, and
adds sparse-material/narrow-overlay test fixtures.
hasLoop becomes user-owned with the gestures as shortcuts onto it; no format change. START uses overlay/trace, not accent/primary, which is the waveform's own fill.
Extracts resolveWaveformClaim (core/instrument/ui/spline_edit) so the shell's node/tab/marker click resolution is unit-tested directly, not just its input geometry; folds the staged-envelope node into it; fixes comment accuracy, a cost regression, and test fidelity issues.
daniel