Every instrument/effect editor gains a "⇄ MIDI" button in its toolbar that opens
a MIDI-learn popup listing the device's adjustable parameters. Tap LEARN on a row,
move a knob/fader on a connected MIDI controller, and its CC binds to that
parameter; the CC's 0..127 sweep then drives the parameter's full range live
(scaled to the spec range, rounded for integer params, nearest choice for enums).
Reuses the existing RawControl path — MidiInput already forwards unbound CCs — so
no parser change was needed. Bindings are stored in the slot's value map under a
reserved `midicc@<param>` key, so they travel with the project/preset and are
thread-safe via the slot's ConcurrentHashMap; one physical control drives one
parameter. Learn is auto-disarmed when the popup or editor closes.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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