Fix capture/record targeting: select real tab (type=page) not extension background page

app.py

@@ -369,16 +369,22 @@ def _launch_chromium(w: int, h: int):
 
 
 async def _connect_cdp(port: int, log):
-    """Wait for the Chrome DevTools websocket URL and return it."""
+    """Wait for the Chrome DevTools websocket URL and return it.
+
+    /json/list returns several targets (extension background pages, browser_ui,
+    etc.). We must pick the actual tab (type == "page") — pages[0] may be an
+    extension background_page, and navigating that would never reach the URL.
+    """
     async with aiohttp.ClientSession() as session:
         for attempt in range(20):
             await asyncio.sleep(0.5)
             try:
                 async with session.get(f"http://localhost:{port}/json/list") as resp:
-                    pages = await resp.json()
-                    if pages:
+                    targets = await resp.json()
+                    page = next((t for t in targets if t.get("type") == "page"), None)
+                    if page:
                         log(f"chrome devtools ready after {attempt+1} attempts")
-                        return pages[0]["webSocketDebuggerUrl"]
+                        return page["webSocketDebuggerUrl"]
             except Exception as e:
                 log(f"devtools attempt {attempt+1} failed: {e}")
                 continue