fix scout_js: reference browser._state not undefined _state

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

tools/scout/src/scout/server.py

@@ -175,8 +175,8 @@ async def scout_js(script: str) -> str:
         "document.querySelector('#onetrust-accept-btn-handler').click(); 'clicked'"
         "Array.from(document.querySelectorAll('button')).map(b=>b.textContent.trim()).join('|')"
     """
-    assert _state["tab"] is not None, "No browser open — call scout_visit first"
-    result = await _state["tab"].execute_script(script)
+    assert browser._state["tab"] is not None, "No browser open — call scout_visit first"
+    result = await browser._state["tab"].execute_script(script)
     return str(result) if result is not None else "(no return value)"