fix(gateway): suppress tool-progress bubbles after interrupt (#16034)

When the LLM response carries N parallel tool calls, the agent fires
N tool.started events back-to-back before its interrupt check runs.
A user sending /stop mid-batch would see the '⚡ Interrupting current
task' ack followed by a trail of 🔍 web_search bubbles for the remaining
events in the batch — making the interrupt feel ignored.

progress_callback and the drain loop in send_progress_messages now
check agent.is_interrupted (via agent_holder[0], the existing
cross-scope handle). Events that arrive after interrupt are dropped
at both the queueing and rendering stages. The '⚡ Interrupting'
message is sent through a separate adapter path and is unaffected.

gateway/run.py

@@ -9370,6 +9370,22 @@ class GatewayRunner:
             if event_type not in ("tool.started",):
                 return
 
+            # Suppress tool-progress bubbles once the user has sent `stop`.
+            # When the LLM response carries N parallel tool calls, the agent
+            # fires N "tool.started" events back-to-back before checking for
+            # interrupts — without this guard, a late `stop` still renders
+            # all N as 🔍 bubbles, making the interrupt feel ignored.
+            # (agent lives in run_sync's scope; agent_holder[0] is the shared
+            # handle across nested scopes — see line ~9607.)
+            try:
+                _agent_for_interrupt = agent_holder[0] if agent_holder else None
+                if _agent_for_interrupt is not None and getattr(
+                    _agent_for_interrupt, "is_interrupted", False
+                ):
+                    return
+            except Exception:
+                pass
+
             # "new" mode: only report when tool changes
             if progress_mode == "new" and tool_name == last_tool[0]:
                 return
@@ -9476,6 +9492,22 @@ class GatewayRunner:
 
                     raw = progress_queue.get_nowait()
 
+                    # Drain silently when interrupted: events queued in the
+                    # window between tool parse and interrupt processing
+                    # should not render as bubbles.  The "⚡ Interrupting
+                    # current task" message is sent separately and is the
+                    # last progress-flavored bubble the user should see.
+                    try:
+                        _agent_for_interrupt = agent_holder[0] if agent_holder else None
+                        if _agent_for_interrupt is not None and getattr(
+                            _agent_for_interrupt, "is_interrupted", False
+                        ):
+                            # Drop this event and continue draining.
+                            await asyncio.sleep(0)
+                            continue
+                    except Exception:
+                        pass
+
                     # Handle dedup messages: update last line with repeat counter
                     if isinstance(raw, tuple) and len(raw) == 3 and raw[0] == "__dedup__":
                         _, base_msg, count = raw