Three targeted fixes for the 'agent stuck on terminal command' report:
1. **Concurrent tool wait loop now checks interrupts** (run_agent.py)
The sequential path checked _interrupt_requested before each tool call,
but the concurrent path's wait loop just blocked with 30s timeouts.
Now polls every 5s and cancels pending futures on interrupt, giving
already-running tools 3s to notice the per-thread interrupt signal.
2. **Cancelled concurrent tools get proper interrupt messages** (run_agent.py)
When a concurrent tool is cancelled or didn't return a result due to
interrupt, the tool result message says 'skipped due to user interrupt'
instead of a generic error.
3. **Typing indicator fires before follow-up turn** (gateway/run.py)
After an interrupt is acknowledged and the pending message dequeued,
the gateway now sends a typing indicator before starting the recursive
_run_agent call. This gives the user immediate visual feedback that
the system is processing their new message (closing the perceived
'dead air' gap between the interrupt ack and the response).
Reported by @_SushantSays.
