feat: stage 2 real CAD conveyor, hybrid physics drops, mobile policy (WIP)

- CAD pipeline: conveer.FCStd -> FreeCAD headless -> conveyor-web.glb
  (555KB Draco, 42 named nodes) integrated into main scene; gates and
  rollers animated from domain state
- Domain-driven adapter sorterVisualState.ts; per-SKU visual physics
  profiles (VISUAL_PHYSICS_ESTIMATE)
- Hybrid Rapier physics: kinematic belt travel -> dynamic drop handoff
  -> verified freeze; shared collider layout (physicsWorldLayout) used
  by runtime and headless validation sim (physicsDropSim + 13 tests)
- Gravity chutes / open roll-cage front redesign (drop tuning in progress:
  4/7 routes verified headless)
- Premium industrial visual: PBR, ACES, PCFSoft shadows, Lightformer env,
  UI cleanup behind ?debug=1
- Mobile capability policy: SVG fallback / Mobile Low / full tiers,
  Telegram WebView forced to SVG, e2e stubs for weak devices
- Performance benchmarks cad-light/physics/full pass; stage2 artifacts

tsc clean. Physics drop validation for 3 SKU routes still in progress.

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

e2e/mobile-fallback.spec.ts

@@ -14,6 +14,14 @@ import { test, expect } from '@playwright/test';
 const MOBILE_UA =
   'Mozilla/5.0 (Linux; Android 13; Pixel 7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Mobile Safari/537.36';
 
+/** Stage 2 §16: fallback tests emulate a WEAK device (capable phones get Mobile Low 3D). */
+async function stubWeakDevice(page: import('@playwright/test').Page) {
+  await page.addInitScript(() => {
+    Object.defineProperty(navigator, 'hardwareConcurrency', { value: 4, configurable: true });
+    Object.defineProperty(navigator, 'deviceMemory', { value: 2, configurable: true });
+  });
+}
+
 function collectErrors(page: import('@playwright/test').Page) {
   const pageErrors: string[] = [];
   const consoleErrors: string[] = [];
@@ -35,6 +43,7 @@ test.describe('mobile fallback (390x844)', () => {
 
   test('shows honest SVG fallback, no false WebGL error, UI stays functional', async ({ page }) => {
     const { pageErrors, consoleErrors } = collectErrors(page);
+    await stubWeakDevice(page);
 
     await page.goto('/');
 
@@ -164,6 +173,40 @@ test.describe('webgl context loss and recovery', () => {
   });
 });
 
+test.describe('stage2 mobile capability policy', () => {
+  test('capable phone gets Mobile Low 3D (no SVG fallback)', async ({ page }) => {
+    const { pageErrors } = collectErrors(page);
+    await page.addInitScript(() => {
+      Object.defineProperty(navigator, 'hardwareConcurrency', { value: 8, configurable: true });
+      Object.defineProperty(navigator, 'deviceMemory', { value: 8, configurable: true });
+    });
+    await page.setViewportSize({ width: 390, height: 844 });
+    await page.goto('/');
+    // Mobile Low mounts the real 3D canvas at low quality
+    await expect(page.locator('canvas')).toBeVisible({ timeout: 60_000 });
+    await expect(page.getByTestId('main-svg-fallback')).toHaveCount(0);
+    await page.getByTestId('demo-play').click();
+    await page.waitForTimeout(4000);
+    expect(pageErrors, `pageerrors: ${pageErrors.join('; ')}`).toEqual([]);
+  });
+
+  test('Telegram WebView is forced to SVG until real-device verification', async ({ page }) => {
+    const { pageErrors } = collectErrors(page);
+    await page.addInitScript(() => {
+      Object.defineProperty(navigator, 'hardwareConcurrency', { value: 8, configurable: true });
+      Object.defineProperty(navigator, 'deviceMemory', { value: 8, configurable: true });
+      // iOS-style Telegram WebView marker
+      (window as unknown as { TelegramWebviewProxy?: unknown }).TelegramWebviewProxy = { postEvent: () => undefined };
+    });
+    await page.setViewportSize({ width: 390, height: 844 });
+    await page.goto('/');
+    const fallback = page.getByTestId('main-svg-fallback');
+    await expect(fallback).toBeVisible({ timeout: 30_000 });
+    await expect(page.locator('canvas')).toHaveCount(0);
+    expect(pageErrors, `pageerrors: ${pageErrors.join('; ')}`).toEqual([]);
+  });
+});
+
 test.describe('stage0 prototype mode', () => {
   test('query params enable cinematic scene; auto cam toggle is truthful', async ({ page }) => {
     const { pageErrors, consoleErrors } = collectErrors(page);

e2e/real-models.spec.ts

@@ -100,6 +100,11 @@ test.describe('Stage 1 real models', () => {
     page.on('request', (req) => {
       if (MODEL_RE.test(req.url())) modelRequests.push(req.url());
     });
+    // Stage 2 §16: fallback path is for weak devices — stub low capability.
+    await page.addInitScript(() => {
+      Object.defineProperty(navigator, 'hardwareConcurrency', { value: 4, configurable: true });
+      Object.defineProperty(navigator, 'deviceMemory', { value: 2, configurable: true });
+    });
 
     await page.goto('/', { waitUntil: 'domcontentloaded' });
     await page.waitForSelector('[data-testid="main-svg-fallback"]', { timeout: 30000 });