Fix secure cookie handling for multi-level subdomains

Disable ThirdPartyStoragePartitioning and PartitionedCookies features
to fix an issue where Chrome fails to properly respect the Secure flag
on cookies set with Domain=.example.com when accessed from multi-level
subdomains like dev.app.example.com.

This resolves the cookie persistence issue documented in #421 where
session cookies were not being sent on subsequent HTTPS requests to
dev.app.example.com despite being set correctly by the server.

Fixes #421

Author: pfergi42

src/browser.ts

@@ -111,6 +111,9 @@ export async function launch(options: McpLaunchOptions): Promise<Browser> {
   const args: LaunchOptions['args'] = [
     ...(options.args ?? []),
     '--hide-crash-restore-bubble',
+    // Fix cookie handling for subdomain patterns (e.g., dev.app.example.com)
+    // Disable third-party cookie partitioning which can interfere with secure cookies
+    '--disable-features=ThirdPartyStoragePartitioning,PartitionedCookies',
   ];
   if (headless) {
     args.push('--screen-info={3840x2160}');