fix: clear request_in_flight when stream ends

Without this, request_in_flight stayed true after tool call streaming,
blocking all subsequent turns until the next completions handler
happened to clear it first.

src/api/completions.rs

@@ -614,6 +614,8 @@ async fn chat_completions_stream(
                         )));
                     }
                     yield Ok(Event::default().data("[DONE]"));
+                    // Clear in-flight flag so the next turn's requests can get through
+                    state.mitm_store.clear_response_async().await;
                     return;
                 }
             }
@@ -869,6 +871,8 @@ async fn chat_completions_stream(
                 Some(build_usage(pt, ct, crt, tt)),
             )));
         }
+        // Always clear in-flight flag when stream ends
+        state.mitm_store.clear_response_async().await;
         yield Ok(Event::default().data("[DONE]"));
     };