feat: Body Canvas V3 body-first workspace

[BakerSean168]

Summary

• replace the consultation shell with the body-first Body Canvas V3 workspace
• add canonical point/brush/box body-region selection, reference motion studio, contextual assistant, equipment inventory, mobile sheets, keyboard access and text fallback
• preserve existing BodyState, Diagnosis, Treatment, Progress and fine Vanatome anatomy as real-data overlays rather than duplicating business truth
• extend the private runtime spatial-context contract with multi-region selection and explicitly non-evidentiary reference_motion
• add the Penpot V3 handoff (4 foundation boards, 12 component boards, 30 product boards / 495 hotspots)
• keep 3D loading lazy and enforce a dedicated Three-only production chunk budget

Safety / semantics

• the home model is a reference body, never represented as a personal scan
• reference animations are teaching/navigation context, not posture measurements or biomechanics evidence
• server normalization validates canonical regions, motion IDs, phase bounds and source=reference_animation
• the Python runtime prompt explicitly prevents selected/animated context from becoming symptoms, load/tension claims or diagnosis

Verification

• pnpm contracts:conformance ✅
• pnpm contracts:check-generated ✅
• Go ./internal/consultation ./internal/service ✅
• Python spatial-context manifest tests: 12 passed ✅
• Body Canvas/reference rig/preferences: 11 passed ✅
• ConsultationPage + Body Explorer workspace/store/adapter/pin: 17 passed ✅
• BodyRegionStatusSummary: 1 passed ✅
• Vite config tests: 4 passed ✅
• pnpm nx typecheck web ✅
• pnpm nx lint web ✅
• pnpm nx build web ✅
• Body Canvas desktop/mobile Playwright: 1/1 passed (24.3s) ✅
• longitudinal business Playwright: 2/2 passed ✅
• Body Explorer heavy WebGL flow: 1/1 passed (5.5m) ✅
• Body Explorer atlas-failure fallback: 1/1 passed (8.5s) ✅
• git diff --check ✅

Production build keeps the default 500 kB budget. The shared lazy Three runtime is explicitly governed at 718.43 kB raw / 181.54 kB gzip; BodyCanvasScene is 21.40 kB raw / 8.45 kB gzip.