Phase 3 / M11: Complete validation, observability, docs, CI, and acceptance #16

Objective

Harden and document the complete Phase 3 system and prove all Phase 1–3 guarantees in automated acceptance and the demonstration session.

Scope

• Add all required control, automation, bus, transition, MIDI, invalid-input, and nREPL fixtures.
• Add RMS, spectral-centroid, pan, click/discontinuity, clipping/silence, NaN/Inf, timing, and trace-correlation validation.
• Run block sizes 64/128/256/512/1024 through shared real-time/offline control behavior.
• Add required unit/integration tests, race scenarios, fuzz targets, and accelerated one-hour stability simulation.
• Add bounded-queue/high-water statistics, structured logs/errors, and control/automation/MIDI/transition traces.
• Add control/automation/MIDI/crossfade benchmarks and enforce/document practical limits and callback budgets.
• Add CLI inspection/validation/render trace flags and Makefile targets from §38.
• Add Phase 3 CI stages and Fedora 44 headless/audio/MIDI/nREPL smoke coverage where facilities exist.
• Write docs/controls.md, automation.md, control-buses.md, midi.md, patch-transitions.md, and nrepl.md; add required examples.
• Run the §43 demonstration and record proof for controls, automation, buses, MIDI, transition migration, nREPL, and offline traces.

Acceptance criteria

• make acceptance-phase3, make acceptance, go test ./..., and go test -race ./... pass.
• Short fuzz runs and stability tests pass with bounded memory/goroutines/lanes and no stuck notes or invalid samples.
• All Phase 3 acceptance criteria in §42 are covered, documentation/dependency/fork information is current, and the repository remains buildable.

Spec: phase-3.md §§26–43 (Milestone 11 and complete Phase 3 acceptance).