Stage 3.5 — Creative:Forge architectural synthesis

> Output of Wave 9 forge pass on the master plan (stage3-expand-master-plan.md). > Scope: deepen the 3 architectural questions the master plan defers or under-specifies. > Treat as **PRODUCTION SYSTEM**. Don't break what ships. > Six forge phases per question: Prime → Explode → Forge → Synthesize → Create → Evolve. The master plan picks the right 5 panes and the right reel-ship cadence, but under-specifies three load-bearing decisions that will bite during Wave A-B execution if not nailed down: - **Q1 — where exactly does the audio tap live, and does LUMF carry SAN's pattern decisions?** Master plan §7.1 hand-waves "AudioEngine pre-allocated buffers" without picking the AVAudioEngine node, the cadence, or the threading model. Get this wrong and either the engine drops audio (catastrophic) or LumfPublisher silently allocates per-buffer (audible glitches every ~5s as ARC stalls the audio thread). - **Q2 — three directors, no shared state schema.** Master plan §6 R6 names the risk ("coordination collapse across 5 panes") but only mitigates code collisions, not director state collisions. Stage 0 found three live directors actively maintained. Without a written contract, the next pane to touch any director re-derives the schema and they diverge harder. - **Q3 — universal sled has two physical constraints (USB topology vs thermal) and four-way mounting variance.** Master plan §7.5 lists `MAC_MINI_W/D/H/FOOT_PITCH` constants but doesn't pick the dominant constraint that drives the CAD geometry. Pick wrong and the sled prints but the cables don't reach, or the thermals are fine but the user fights connectors every load-in.