fix(streaming): update stale-stream timer during Anthropic native streaming (#7117)

The _call_anthropic() streaming path never updated last_chunk_time during
the event loop — only once at stream start. The stale stream detector in
the outer poll loop uses this timer, so any Anthropic stream longer than
180s was killed even when events were actively arriving. This self-inflicted
a RemoteProtocolError that users saw as:

  '⚠️ Connection to provider dropped (RemoteProtocolError). Reconnecting…'

The _call_chat_completions() path already updates last_chunk_time on every
chunk (line 4475). This brings _call_anthropic() to parity.

Also adds deltas_were_sent tracking to the Anthropic text_delta path so
the retry loop knows not to retry after partial delivery (prevents
duplicated output on connection drops mid-stream).

Reported-by: Discord users (Castellani, Codename_11)

run_agent.py

@@ -4692,6 +4692,14 @@ class AIAgent:
             # Use the Anthropic SDK's streaming context manager
             with self._anthropic_client.messages.stream(**api_kwargs) as stream:
                 for event in stream:
+                    # Update stale-stream timer on every event so the
+                    # outer poll loop knows data is flowing.  Without
+                    # this, the detector kills healthy long-running
+                    # Opus streams after 180 s even when events are
+                    # actively arriving (the chat_completions path
+                    # already does this at the top of its chunk loop).
+                    last_chunk_time["t"] = time.time()
+
                     if self._interrupt_requested:
                         break
 
@@ -4715,6 +4723,7 @@ class AIAgent:
                                 if text and not has_tool_use:
                                     _fire_first_delta()
                                     self._fire_stream_delta(text)
+                                    deltas_were_sent["yes"] = True
                             elif delta_type == "thinking_delta":
                                 thinking_text = getattr(delta, "thinking", "")
                                 if thinking_text: