One header per mode, each ~50-130 LOC built atop ModeBase:
- `paf_synth.hpp` (4 inputs → 33 outputs, 7 voice spaces, note_on/off)
- `channel_strip.hpp` (4 → 24, 6 voice spaces)
- `xiasri.hpp` (4 → 24, 1 'Direct' voice space)
- `verb_fx.hpp` (4 → 47, 12 voice spaces)
- `memlcelium.hpp` (4 → 56, dual synth + 2-track sequencer; set_playing/update_bpm)
- `breakor.hpp` (4 → 56, 8-track ratio sequencer; pumps engine NoteOn/Off/Clock
events into ControlEvent ring buffer)
- `elysiamorf.hpp` (4 → 40, 8-track FM-pair MIDI-CC sequencer; pumps CC events)
- `sound_analysis_midi.hpp` (10 → 8; owns AnalysisEngine for input feature
extraction PLUS NoOpEngine 'thru' for audio passthrough; ML outputs
converted to MIDI CC events via on_post_inference; opts out of
output→engine routing via ModeRoutesOutputsToEngine specialisation)
Every mode satisfies `nisps::Mode` (verified via `static_assert` in each
header). Schema `output_size` is verified against engine `param_count()`
at compile time inside ModeBase.
All hardware-specific glue (MEMLNaut::Instance, pico/util/queue, MIDIInOut,
display widgets, button callbacks) is intentionally absent — that lives in
firmware/glue and playground/src/modes per architecture.md §4.3.
