- Remove ~700 lines of legacy code from app.py (run_demo_mode, run_pipeline_demo,
run_preset_mode, font picker, effects picker)
- HUD now reads metrics from pipeline context (first-class citizen) with fallback
to global monitor for backwards compatibility
- Add validate_signal_flow() for PureData-style type validation in presets
- Update MicSensor documentation (self-contained, doesn't use MicMonitor)
- Delete test_app.py (was testing removed legacy code)
- Update AGENTS.md with pipeline architecture documentation
- Convert presets from YAML to TOML format (no external dep)
- Add DEFAULT_PRESET fallback for graceful degradation
- Add validate_preset() for preset validation
- Add validate_signal_path() for circular dependency detection
- Add generate_preset_toml() for skeleton generation
- Use tomllib (Python 3.11+ stdlib)
