Move the Arduino sketch into firmware/MEMLNaut-NISPS/ and bridge the
hardware (memllib) to the platform-agnostic nisps/ library through a
slim glue layer. Delete the legacy root-level *AudioApp.hpp,
modes/MEMLNautMode*.hpp, voicespaces/, IMLInterface.hpp, XiasriAnalysis,
and the src/memlp submodule.
Glue layout (firmware/MEMLNaut-NISPS/glue/):
audio_driver.hpp - bridge memllib block callback to Mode::process
via per-Mode templated trampoline (no virtual dispatch)
peripherals.hpp - joystick/pots/buttons -> Mode::set_input + ML primitives
midi_io.hpp - MIDI in -> mode.note_on/update_bpm/set_playing,
drains mode ControlEvent ring -> MIDI UART
mode_select.hpp - using-aliases mapping MEMLNautMode<Name> to
nisps::modes::*Mode (build script rewrites the
#define MEMLNAUT_MODE_TYPE line)
input_router.hpp / output_router.hpp - top-level wire/drain entry points
The sketch tree uses src/{memllib,daisysp,nisps} symlinks because
Arduino-CLI rejects ".." in include paths from sketch-tree headers.
mode_select.hpp #undefs Arduino's sq/min/max/abs/round macros before
including nisps headers (some nisps engines use those identifiers as
method names). The audio bridge struct is extern in the header and
defined in the .ino because inline + __not_in_flash section attribute
collide at link time.
Verification: arduino-cli compile succeeds for PAFSynth, ChannelStrip,
and BreakOr (rp2040:rp2040:solderparty_rp2350_stamp_xl:opt=Optimize3,
-std=gnu++20). Host C++ tests under nisps/build still pass (3 binaries,
110+ tests). Build script (scripts/build-firmware.sh) updated to point
at the new sketch path; mode-rewrite logic unchanged.
Closes meml-gkm.
