Add Firefox cookie import and stealth mode

- Firefox cookie importer: reads cookies.sqlite with WAL-safe copy,
  profile detection via profiles.ini, cross-platform paths, domain filtering
- Stealth mode: opt-in via launch(stealth: true), patches navigator.webdriver,
  plugins/mimeTypes, permissions API, WebGL renderer, iframe isolation,
  languages, plus realistic Safari UA and context hardening
- Import tool now accepts 'safari' | 'firefox' source
- STEALTH.md reference documentation
- Upgraded @types/node to v25 for node:sqlite support

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@saiden/browse",
-  "version": "0.2.20",
+  "version": "0.2.20-8ca7263",
   "description": "Headless browser automation for Claude Code using Playwright WebKit",
   "type": "module",
   "main": "dist/index.js",
@@ -56,7 +56,7 @@
   },
   "devDependencies": {
     "@biomejs/biome": "^1.9.0",
-    "@types/node": "^20.11.0",
+    "@types/node": "^25.6.0",
     "@types/sharp": "^0.31.1",
     "@vitest/coverage-v8": "^4.0.18",
     "tsx": "^4.21.0",