ci: hold the page to its Lighthouse budget

.github/workflows/ci.yml

@@ -29,3 +29,28 @@ jobs:
       - run: pnpm install --frozen-lockfile
       - run: pnpm check
       - run: pnpm build
+
+  # The page's budget: 100 in Lighthouse, with a little slack for the runner. Its own job, so a slow
+  # runner never hides a type error, and the reports are kept either way.
+  lighthouse:
+    name: Lighthouse
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
+      - uses: pnpm/action-setup@fc06bc1257f339d1d5d8b3a19a8cae5388b55320 # v4.4.0
+        with:
+          version: 12.16.0
+      - uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5.0.0
+        with:
+          node-version: 24.22.2
+          cache: pnpm
+      - run: pnpm install --frozen-lockfile
+      - run: pnpm build
+      - run: pnpm lighthouse
+      - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        if: always()
+        with:
+          name: lighthouse-reports
+          path: lighthouse-reports/
+          retention-days: 14

.gitignore

@@ -2,3 +2,4 @@ dist/
 node_modules/
 .astro/
 .DS_Store
+lighthouse-reports/

README.md

@@ -19,8 +19,10 @@ pnpm build    # dist/
 The 3D scene (`src/scripts/landing/scene.ts`) runs in a Web Worker on an OffscreenCanvas where the
 browser supports it, and on the page otherwise; `scene-client.ts` decides and `scene-worker.ts` is the
 worker. Either way the page paints its hero on the first frame and never blocks on three.js, which is
-what keeps Lighthouse at 100 on mobile. Measure with `pnpm build && pnpm preview` and Lighthouse
-against `http://localhost:4321/`; the Cloudflare beacon is the one request that fails offline.
+what keeps Lighthouse at 100 on mobile. `pnpm build && pnpm lighthouse` measures it the way CI does
+(`scripts/lighthouse.mjs`: the mobile default and the desktop preset, median of three runs, reports in
+`lighthouse-reports/`) and fails under the budget set there: 95 in performance, 100 in the rest. The
+Cloudflare beacon is kept out of the audit, so the check works offline and never fails on a third party.
 
 pnpm, like the framework repository, and not only for consistency: `npm ci` cannot install this
 tree on Linux from a lockfile resolved on macOS, because rolldown ships its native bindings as

package.json

@@ -7,7 +7,8 @@
     "dev": "astro dev --host",
     "build": "astro build",
     "check": "astro check",
-    "preview": "astro preview"
+    "preview": "astro preview",
+    "lighthouse": "node scripts/lighthouse.mjs"
   },
   "dependencies": {
     "astro": "7.4.2",
@@ -17,6 +18,7 @@
     "@astrojs/check": "0.9.12",
     "@astrojs/sitemap": "3.7.4",
     "@types/three": "0.186.0",
+    "lighthouse": "13.6.0",
     "typescript": "5.9.3",
     "wrangler": "4.152.0"
   }