Complete networking integration gate (#58)

docs/caps-http.md

@@ -89,6 +89,10 @@ statuses and transport failures retry up to the request's configured retry
 count with bounded backoff. Disposal cancels active and queued work, wakes every
 waiter, joins the dispatcher, and prevents new requests.
 
+`DownloadManager::active_download_count`, `dispatcher_running`, and
+`is_disposed` expose payload-free lifecycle state for leak assertions. They do
+not expose capability URIs or response data.
+
 Errors expose only typed categories and `Debug` output substitutes a redacted
 marker for capability URIs. No request URL, query token, body, or response body
 is logged.