fix(qa): don't pass the macOS-only Metal ANGLE backend on other platforms

Six QA harnesses launched Chrome with `--use-angle=metal` unconditionally
(or defaulted to it). Metal is a macOS-only ANGLE backend: on Windows and
Linux it makes WebGL initialization fail outright, so CesiumWidget never
constructs, the app never boots, and the harness dies at its
`waitForFunction` boot wait — before running a single assertion:

    Error constructing CesiumWidget.
    RuntimeError: The browser supports WebGL, but initialization failed.
    TimeoutError: Waiting failed: 60000ms exceeded

Affected: qa-map-source-tray, qa-cockpit-utility, qa-view-target-prewarm,
qa-firstrun (unconditional), qa-cockpit-plates (GPU branch taken off-Mac
too) and qa-floor-hold (`--angle` defaulted to metal everywhere).

Fixed by adopting the platform check qa-flyroute-cinema.mjs already uses:
real GPU via Metal on darwin, the portable swiftshader rasterizer
elsewhere — which is what the other ~20 QA scripts already pass. No
behavior change on macOS.

Verified on Windows 11: `npm run qa:map-source-tray` went from 0
assertions (boot timeout) to all 20 checks running.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01C3eGYgDYBo2BCUeDGwGvrp

scripts/qa-cockpit-plates.mjs

@@ -222,7 +222,9 @@ async function main() {
     args: [
       '--no-sandbox',
       '--disable-setuid-sandbox',
-      ...(SWIFTSHADER
+      // Metal is a macOS-only ANGLE backend; off-Mac the GPU branch has to fall
+      // back to the software rasterizer or WebGL init fails outright.
+      ...(SWIFTSHADER || process.platform !== 'darwin'
         ? ['--use-gl=angle', '--use-angle=swiftshader']
         : ['--use-angle=metal', '--enable-gpu', '--ignore-gpu-blocklist']),
       '--disable-dev-shm-usage',

scripts/qa-cockpit-utility.mjs

@@ -20,7 +20,13 @@ const executablePath = chromeCandidates.find((candidate) => fs.existsSync(candid
 const browser = await puppeteer.launch({
   headless: headful ? false : 'new',
   ...(executablePath ? { executablePath } : {}),
-  args: ['--use-angle=metal', '--enable-gpu', '--no-sandbox'],
+  // Metal is a macOS-only ANGLE backend; anywhere else it fails WebGL init.
+  args: [
+    ...(process.platform === 'darwin'
+      ? ['--use-angle=metal', '--enable-gpu']
+      : ['--use-gl=angle', '--use-angle=swiftshader']),
+    '--no-sandbox',
+  ],
 });
 const page = await browser.newPage();
 const failures = [];

scripts/qa-firstrun.mjs

@@ -491,7 +491,10 @@ async function main() {
     ...(executablePath ? { executablePath } : {}),
     args: [
       '--no-sandbox', '--disable-setuid-sandbox',
-      '--use-angle=metal', '--enable-gpu', '--ignore-gpu-blocklist',
+      // Metal is a macOS-only ANGLE backend; anywhere else it fails WebGL init.
+      ...(process.platform === 'darwin'
+        ? ['--use-angle=metal', '--enable-gpu', '--ignore-gpu-blocklist']
+        : ['--use-gl=angle', '--use-angle=swiftshader']),
       '--disable-dev-shm-usage', '--disable-background-timer-throttling',
       '--disable-renderer-backgrounding', '--window-size=1440,900',
     ],

scripts/qa-floor-hold.mjs

@@ -37,7 +37,8 @@ import path from 'node:path';
 const APP_URL = process.env.QA_BASE_URL || 'http://localhost:4173';
 const argv = Object.fromEntries(process.argv.slice(2)
   .map((a) => a.replace(/^--/, '').split('=')).map(([k, v]) => [k, v ?? true]));
-const ANGLE = String(argv.angle || 'metal');
+// Metal is a macOS-only ANGLE backend; defaulting to it off-Mac fails WebGL init.
+const ANGLE = String(argv.angle || (process.platform === 'darwin' ? 'metal' : 'swiftshader'));
 const HEADFUL = !!argv.headful;
 // Austin airport apron by default — the site qa-floor-verify pins, where the
 // mesh sits ~150 m above the geoid and burial is unmistakable.

scripts/qa-map-source-tray.mjs

@@ -29,7 +29,15 @@ fs.mkdirSync(shotsDir, { recursive: true });
 const browser = await puppeteer.launch({
   headless: headful ? false : 'new',
   executablePath,
-  args: ['--use-angle=metal', '--enable-gpu', '--no-sandbox'],
+  // Metal is a macOS-only ANGLE backend: passing it on Windows or Linux makes
+  // WebGL initialization fail outright, so Cesium never constructs and this
+  // harness dies at the boot wait before a single assertion runs.
+  args: [
+    ...(process.platform === 'darwin'
+      ? ['--use-angle=metal', '--enable-gpu']
+      : ['--use-gl=angle', '--use-angle=swiftshader']),
+    '--no-sandbox',
+  ],
 });
 const page = await browser.newPage();
 const failures = [];

scripts/qa-view-target-prewarm.mjs

@@ -39,7 +39,13 @@ const executablePath = chromeCandidates.find((candidate) => fs.existsSync(candid
 const browser = await puppeteer.launch({
   headless: headful ? false : 'new',
   ...(executablePath ? { executablePath } : {}),
-  args: ['--use-angle=metal', '--enable-gpu', '--no-sandbox'],
+  // Metal is a macOS-only ANGLE backend; anywhere else it fails WebGL init.
+  args: [
+    ...(process.platform === 'darwin'
+      ? ['--use-angle=metal', '--enable-gpu']
+      : ['--use-gl=angle', '--use-angle=swiftshader']),
+    '--no-sandbox',
+  ],
 });
 const page = await browser.newPage();
 const failures = [];