fix(browse): bump Playwright to ^1.60.0 and pin full Chromium for extension loading

Two related fixes:

1. Playwright bump ^1.58.2 → ^1.60.0 (Chromium 1208/Chrome 145 → 1223/Chrome 148).
   Chromium 1208 fails Flutter Web's FlutterLoader environment compatibility check
   in headless mode, producing blank pages with webgl:false and no flt-glass-pane.
   Chromium 1223 (1.60.0) renders Flutter 3.41+ apps correctly in headless.
   Verified empirically: same browse source, same args, only Chromium build differs.

2. launchHeaded() now explicitly passes executablePath: executablePath ||
   chromium.executablePath() to launchPersistentContext. Playwright 1.49 changed
   headless:true to use chrome-headless-shell (which cannot load extensions).
   The headed path was unaffected, but we were relying on that implicitly. This
   pin ensures /open-gstack-browser and /pair-agent keep loading the sidebar
   extension if Playwright ever changes launchPersistentContext defaults.

GSTACK_CHROMIUM_PATH still takes priority in both paths.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: stevenbarragan

browse/src/browser-manager.ts

@@ -418,7 +418,10 @@ export class BrowserManager {
       args: launchArgs,
       viewport: null,  // Use browser's default viewport (real window size)
       userAgent: this.customUserAgent || customUA,
-      ...(executablePath ? { executablePath } : {}),
+      // Playwright 1.49+ defaults headless:true to chrome-headless-shell, which
+      // cannot load Chrome extensions. Explicitly pin the full Chromium binary
+      // so future Playwright upgrades don't silently break /open-gstack-browser.
+      executablePath: executablePath || chromium.executablePath(),
       ...(this.proxyConfig ? { proxy: this.proxyConfig } : {}),
       // Playwright adds flags that block extension loading
       ignoreDefaultArgs: [

bun.lock

@@ -47,7 +47,8 @@
     "@ngrok/ngrok": "^1.7.0",
     "diff": "^7.0.0",
     "marked": "^18.0.2",
-    "playwright": "^1.58.2",
+    "playwright": "^1.60.0",
+    "playwright-core": "^1.60.0",
     "puppeteer-core": "^24.40.0",
     "socks": "^2.8.8"
   },