Add cross-platform support to browser-tools

[tarrencev]

Summary

• Adds platform detection for Chrome executable and profile paths (macOS, Linux, Windows)
• Auto-discovers Chrome/Chromium from common installation locations on each platform
• Supports CHROME_PATH and CHROME_PROFILE_PATH environment variables for custom setups
• Improves error messages when Chrome or profile is not found

[lsj5031]

Great cross-platform work! One suggestion: Windows profile syncing still won't work since rsync isn't available. Consider using robocopy for Windows:

if (platform() === "win32") {
  execSync(`robocopy "${profilePath}" "${SCRAPING_DIR}" /MIR /XF SingletonLock SingletonSocket SingletonCookie /XD Sessions`, { stdio: "pipe" });
} else {
  // existing rsync code
}