fix(wire): reject steer messages after turn ends

[howardpen9]

Summary

• Fix a race condition in WireServer._handle_steer() where steer messages sent after run_soul() returns but before _cancel_event cleanup would be accepted with status=steered but never consumed — silently lost
• Add _turn_active flag to precisely track soul execution lifecycle, replacing the _is_streaming check (which relied on _cancel_event is not None) for steer gating
• Add test covering the tail-window race scenario

Problem

_is_streaming is derived from _cancel_event is not None. Since _cancel_event is only cleared in the finally block of _handle_prompt(), there's a window between run_soul() returning and the finally cleanup where:

1. Client receives TurnEnd event
2. Client sends a steer message
3. _handle_steer() sees _is_streaming == True and accepts it
4. soul.steer() queues the message
5. But the turn is already over — the steer is never consumed
6. At next turn start, _agent_loop() discards it as "stale"

Since _read_loop() dispatches inbound JSON-RPC messages concurrently via asyncio.create_task, the ordering between _handle_prompt's finally block and _handle_steer is scheduler-dependent.

Fix

Add a _turn_active: bool flag that is:

• Set to True when _handle_prompt() starts run_soul()
• Set to False immediately when run_soul() returns (before finally cleanup)

_handle_steer() now checks _turn_active instead of _is_streaming, closing the tail window.

Test plan

• New test: test_handle_steer_rejects_after_turn_ends — simulates the exact race window
• Existing test updated: test_handle_steer_queues_input_when_streaming — sets _turn_active = True
• All 6 wire server steer tests pass
• All 12 kimisoul steer tests pass

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.