Bug: PedalApp._on_midi_cc() received (value, channel) where channel was
the MIDI channel (0-15) but was treated as the CC number (0-127). The
register_cc callback only passes value + MIDI channel, not the CC number.
Fix: Use a lambda closure in _wire_midi_callbacks to capture the CC
number so _on_midi_cc gets (value, cc_number, channel). Moved expression
pedal (CC#11) check before the presets/pipeline guard so it works even
when no preset is active.
Tests: 21 new integration tests covering:
- CC lambda closure capturing correct CC numbers
- Expression pedal → master volume (CC#11)
- Full parse→dispatch→callback chain for PC and CC
- Preset MIDI mapping lookup by CC number
- Edge cases: min/max values, rapid switching, empty slots
