Invariants — Rules That Must Never Be Violated

These constraints are drawn from all three documentation sets (Set A implementation, Set B AirDeck/camera-first, Set C Mac4 manuscript). Violation causes either system failure, safety risk, or loss of artistic integrity. **I-1: Only K11 sends Rekordbox commands.** Unity, mocopi, Mac4 browser, MotionMix, iPhones, and Watch must not directly dispatch Rekordbox keyboard or MIDI events. K11's command gate is the sole authority. **I-2: No gesture becomes live without promotion.** A newly detected gesture cannot fire a Rekordbox command without passing through the full promotion pipeline (physical capture → capture gate → self-play → proof matrix → promotion manifest loaded by K11 bridge). Exception: left hand raise (deck 1) and right hand raise (deck 2) are baseline proven gestures and may remain live. **I-3: EchelonHandle is MainActor-only.** The Rust FFI handle must only be accessed from Swift's MainActor. Any other thread produces undefined behavior in the Rust core. **I-4: AudioHandle is audio-thread-only.** `renderAudio()` must never be called from MainActor. The audio thread is real-time; any allocation or GC pause causes audible glitches.