Echelon Implementation Plan

## Summary - Translate the architecture alignment brief into actionable engineering work, ensuring the Rust engine, scheduler, AI sidecars, and UI land in lockstep with the 24-week delivery timeline. - This plan tracks sprint-level execution with explicit dependencies, acceptance criteria, and hand-off milestones. ### Phase 0 – Kickoff (Week 0) - Confirm workstream leads and staffing matrix. - Stand up new Rust workspace CI (lint, fmt, unit tests) and latency profiling harness. - Baseline decision log: IPC protocol choice, UI framework (egui vs iced), licensing plan for external libs. ### Phase 1 – Engine Bring-up (Weeks 1-6) - **Audio IO Layer** - Implement `cpal` backend for macOS; stub Linux/Windows modules. - Add real-time audio callback with double-buffered channel ring. - Acceptance: sine test tone with measured round-trip latency <10 ms. - **Sample Graph & Deck Nodes** - Define lock-free node arena and preallocation strategy. - Implement dual deck players with cue points, crossfade envelope. - Acceptance: load two test WAVs, perform seamless crossfade under profiler. - **Mixer & Mastering** - Add per-deck EQ, filter stubs, master limiter using proven coefficients. - Run continuous profiling to confirm no allocations on the audio thread. ### Phase 2 – Scheduler & Safety (Weeks 7-12) - **Transport & Link** - Integrate Ableton Link SDK; expose beat clock and transport state. - Implement quantized action executor with configurable beat resolution. - **Safety Policies** - Port DJ Agent deck lock, cooldown, and action mask logic into Rust. - Mirror Python regression tests with Rust property-based tests. - **MIDI & External Control** - Create virtual MIDI port and learning hooks; map baseline actions. - Acceptance: manual MIDI controller triggers quantized play/loop without violating safety constraints. ### Phase 3 – AI & Human Interfaces (Weeks 13-18) - **Motion & Voice** - Wrap DELL bridge (FFI or IPC) to stream normalized motion features. - Integrate `whisper-rs` command recognizer with confirmation UX. - **Phrase Intelligence** - Expose Episode 1 embeddings and ANN search as Rust service or IPC sidecar. - Implement crate builder suggestions aligned with rehearsal flow. - **UI Surface** - Build egui/iced performance deck (two decks, phrase browser, automation curves, telemetry meters). - Conduct usability sessions; fix critical feedback before Beta sign-off. - **Visualization** - Implement `crates/viz` library per `docs/visualize.md` with PCA/parametric projection, beat-phase halo, residual glow, attractor disk, and limb satellites. - Extend `control-bus` with `FastState`, `SlowState`, and `Telemetry` structs plus decimated SPSC ring for visualization subscribers. - Embed viz as optional egui widget and standalone window; guard behind `viz` ca