fix: restore token in /health for localhost extension auth

The CSO security fix stripped the token from /health to prevent leaking
when tunneled. But the extension needs it to authenticate on localhost.
Now returns token only when not tunneled (safe: localhost-only path).

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

browse/src/server.ts

@@ -1290,7 +1290,9 @@ async function start() {
         };
         // Sensitive fields only served on localhost (not through tunnel).
         // currentUrl reveals internal URLs, currentMessage reveals user intent.
+        // token needed by extension to authenticate subsequent requests.
         if (!tunnelActive) {
+          healthResponse.token = AUTH_TOKEN;
           healthResponse.currentUrl = browserManager.getCurrentUrl();
           healthResponse.chatEnabled = true;
           healthResponse.agent = {