Fix: correct Playwright Docker tag, sequential Lighthouse audits, devtools throttling

- Pin playwright npm to 1.59.1 to match Docker image tag
- Update base image to mcr.microsoft.com/playwright:v1.59.1-jammy
- Run Lighthouse desktop and mobile sequentially (parallel caused port conflict)
- Switch to devtools throttling (simulate caused LanternError on localhost)
- Skip browser download during npm ci (image has browsers pre-installed)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -1,10 +1,10 @@
-FROM mcr.microsoft.com/playwright/node:20-noble
+FROM mcr.microsoft.com/playwright:v1.59.1-jammy
 
 WORKDIR /app
 
 # Install dependencies first (layer cache)
 COPY package*.json ./
-RUN npm ci --omit=dev
+RUN PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD=1 npm ci --omit=dev
 
 # Copy source
 COPY src/ ./src/

package.json

@@ -11,7 +11,7 @@
   "dependencies": {
     "chrome-launcher": "^1.1.2",
     "lighthouse": "^12.2.1",
-    "playwright": "^1.44.0"
+    "playwright": "1.59.1"
   },
   "engines": {
     "node": ">=20"

src/index.js

@@ -39,7 +39,6 @@ async function main() {
 
     // Stage 2 & 3: Lighthouse desktop + mobile
     console.log('Running Lighthouse desktop audit...');
-    console.log('Running Lighthouse mobile audit...');
     const lighthouseResults = await runLighthouse(url, rawDir);
 
     // Stage 4: Report assembly

src/lighthouse.js

@@ -65,7 +65,7 @@ async function runPreset(url, preset, rawDir) {
   const chromePath = chromium.executablePath();
   const chrome = await launch({
     chromePath,
-    chromeFlags: ['--headless=new', '--no-sandbox', '--disable-gpu', '--disable-dev-shm-usage'],
+    chromeFlags: ['--headless', '--no-sandbox', '--disable-gpu', '--disable-dev-shm-usage'],
   });
 
   try {
@@ -82,7 +82,7 @@ async function runPreset(url, preset, rawDir) {
         deviceScaleFactor: isDesktop ? 1 : 2,
         disabled: false,
       },
-      throttlingMethod: 'simulate',
+      throttlingMethod: 'devtools',
       onlyCategories: ['performance', 'accessibility', 'best-practices', 'seo'],
     };
 
@@ -116,10 +116,9 @@ async function runPreset(url, preset, rawDir) {
 }
 
 export async function runLighthouse(url, rawDir) {
-  const [desktop, mobile] = await Promise.all([
-    runPreset(url, 'desktop', rawDir),
-    runPreset(url, 'mobile', rawDir),
-  ]);
+  const desktop = await runPreset(url, 'desktop', rawDir);
+  console.log('Running Lighthouse mobile audit...');
+  const mobile = await runPreset(url, 'mobile', rawDir);
   return [desktop, mobile];
 }