P4: MIDI control surface mapping — faders/buttons over USB MIDI
C++ backend (fully implemented):
- MidiMapper: CC processing, mapping table, JSON persistence, learn mode
- MidiLearnMode: 3-step learn workflow state machine
- MixerEngine::processMidiEvent() wired into AudioHost MIDI pipeline
- MixerApi + PiPedalSocket: all WS handlers (getMidiMappings,
setMidiLearnMode, setMidiLearnTarget, commitMidiLearn, etc.)
React frontend (new):
- MidiMappingPanel: dialog with learn mode toggle, CC capture polling,
commit workflow, current mappings list with delete, manual add
- MixerPage: MIDI button in toolbar, learn mode state management
- ChannelStrip + MasterBus: learn mode callbacks on fader/mute/solo touch
shawn
5fd5946ff6