chore: consolidate documentation and clean repository

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/ENGINEERING.md

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+# Engineering notes (canonical)
+
+Companion to `README.md` and `/documentation`. Not a stage changelog.
+
+## Coordinate conventions
+
+- World units: **1 unit = 1 meter**.
+- Belt travel primarily along **+X**; belt top Y ≈ **0.70 m**.
+- Lateral: **+Z** = physical LEFT (category C), **−Z** = physical RIGHT (category D).
+- Sorter CAD module origin X = `0`; camera module `−2.01`; clean module `−4.02`.
+- Longitudinal plane S for diverter timing is world X along the sorter module.
+
+## Canonical constants (code)
+
+| Symbol | Value | File |
+|---|---|---|
+| `DIVERTER_LEFT_SIGNED_DEG` | −45 | `src/domain/pusherMotion.ts` |
+| `DIVERTER_RIGHT_SIGNED_DEG` | +45 | same |
+| `rotationDurationSec()` | 0.50 | same (45° / 90°/s) |
+| `OPENING_SAFETY_MARGIN_SEC` | 0.15 | same |
+| Contact / clear planes | ≈1.0538 / 1.6000 | `buildDiverterPlanes` + mount hinge |
+| Classifier min/max | exclusive 10³ / 450×320×320 | `src/domain/classifier.ts` |
+| Roundness | K > 0.8 | same |
+| `CONVEYOR_CAD_URL` | `/models/sorter/conveyor-clean.glb` | `ConveyorCadModel.tsx` |
+
+## Active source tree (runtime)
+
+```
+src/main.tsx
+src/App.tsx
+src/pages/{MainPage,DocumentationPage}.tsx
+src/components/{AppNav,SorterScene,CVInspectionOverlay,BuildIdentityBadge}.tsx
+src/components/ThreeD/* (active twin only)
+src/domain/* (classifier, playback, layout, diverter, physics helpers)
+src/data/{items,modelAssets,resolveItem,productionStatusSummary,demoPlaylist,scenarios}.ts
+src/styles.css
+```
+
+## Asset provenance
+
+| Role | Path |
+|---|---|
+| Author CAD | `3d_models/conveer.FCStd` |
+| Runtime conveyor | `public/models/sorter/conveyor-clean.glb` |
+| Products | `public/models/*.stl` from official STL ZIP |
+| Classifier PDF | `official_sources/doc-1783095831.pdf` |
+| Workspace / scoring PDFs | `input_info/doc-1783009942.pdf`, `doc-1783011400.pdf` |
+
+## Physics roadmap (not completed)
+
+1. Surface-velocity belt at 1 m/s with visual loop.
+2. Contact-validated CAD diverter deflection for all playlist SKUs.
+3. Calibrated per-SKU mass, COM, friction, damping.
+4. Receiver capture verification under dynamic drops.
+
+CCD for light/thin items exists in runtime/sim; that alone is **not** full contact validation.
+
+## Compliance evidence rules
+
+- Prefer present official files under `input_info/` and `official_sources/doc-1783095831.pdf`.
+- Missing: `input_info/extracted/Постановка_Задача_3_сжато_2.pdf` — never claim it is available.
+- Internal engineering criteria are not automatic Ozon pass/fail.
+
+## Layout drawing
+
+`docs/engineering/work-area-layout-source.png` — workspace layout provenance image retained for engineering reference.