Wires the click-to-insert into the GUI: a pencil ("insert") mode, toggled by a
toolbar button or the P key, turns a staff click into insert_note_at on a
default quarter-note grid (make-room overwrite), instead of selecting. A
non-pencil click still selects, and its empty-staff status now reports what a
pencil click would insert (pitch + grid-snapped beat).
The pencil edit runs in score_view, after the frame's rerender slot, so it
requests a repaint and returns before the selection overlay would paint the new
hit map over the not-yet-rerendered texture. Non-pencil selection keeps the
immediate overlay path (it does not mutate the rendered score).
This completes the beat-grid click-to-insert feature (vertical inverse →
horizontal inverse → trim/move reducer semantics → insert_note_at → this GUI
wiring). The GUI's rendering/interaction is still not visually verifiable in
this environment; only the ViewMap coordinate logic is unit-tested.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NAtEiJtt9yKVV1zjKYmZhS
Levi Neuwirth
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