test(nisps/modes): host C++ tests for stream 4 mode layer (meml-beb)
Adds `nisps_modes_tests` executable to nisps/CMakeLists.txt with four TUs:
- `test_mode_concepts.cpp`: 8 `static_assert(Mode<...>)` (concept
satisfaction), plus runtime metadata sanity for each mode (mode_id,
input_channel_count, schema sizes match engine param_count).
- `test_mode_paf_synth.cpp`: end-to-end exercise — setup, set_input,
tick_control, process audio. Verifies idle process is finite, output
bounds [0,1] hold, note_on triggers nonzero audio, input clamping,
and engine/ml accessors round-trip.
- `test_mode_voice_space.cpp`: voice-space round trip for PAFSynth,
ChannelStrip and VerbFX (all dispatched modes). Confirms
out-of-range index is silently ignored.
- `test_mode_breakor_events.cpp`: sequencer event pumping. BreakOr
emits Clock + NoteOn/Off, Elysiamorf emits CC, SoundAnalysisMIDI
converts 8 ML outputs → 8 ControlEvents (CC 0..7) per tick, ring
buffer overflow drops cleanly.
Total: 22 new tests (110 across nisps/), all passing under -Werror
-Wpedantic. Build remains clean.
4964037da0