Swallow sandbox container races in the stream consumer

[0xallam]

When the TUI quit path SIGKILL's the sandbox container (PR #548), the agent's in-flight SDK calls can race the cleanup and surface as either:

• agents.sandbox.errors.ExecTransportError — from exec calls into the now-gone container
• docker.errors.NotFound — from container.reload() / inspect_container / any container lookup

Both are expected during teardown. Catch them in _run_cycle's stream consumer alongside the existing LiteLLM shutdown-race catch.

Also moves the raise stream.run_loop_exception line inside the try, so the stored exception path is covered too (the SDK stashes the exception on the stream object rather than re-raising it through stream_events()).

[greptile-apps]

Greptile Summary

This PR addresses teardown races introduced by PR #548's SIGKILL sandbox cleanup by catching ExecTransportError and docker.errors.NotFound in _run_cycle's stream consumer, guarded by a new coordinator.is_shutting_down flag that is set at the start of _fire_sandbox_cleanup.

• Adds is_shutting_down to AgentCoordinator and mark_shutting_down() call in _fire_sandbox_cleanup, so swallowing is correctly scoped to TUI-initiated teardown rather than unconditional.
• Moves raise stream.run_loop_exception inside the try block so stored exceptions (stashed on the stream object by the SDK) are covered by all three except clauses.
• The new except clause includes exc_info=True, preserving tracebacks for post-mortem debugging of teardown noise.

Confidence Score: 5/5

Safe to merge — the change is narrowly scoped to teardown races and the swallowing is properly gated on the shutdown flag.

Both concerns raised in earlier review rounds have been addressed: the coordinator.is_shutting_down guard ensures genuine container crashes outside teardown are still surfaced, and exc_info=True preserves tracebacks. The flag is set before the SIGKILL fires, the exception paths are correctly covered, and non-TUI shutdown paths are unaffected.

No files require special attention.

Important Files Changed

Filename	Overview
strix/core/agents.py	Adds is_shutting_down flag and mark_shutting_down() method to AgentCoordinator to gate sandbox-error swallowing in the stream consumer.
strix/core/execution.py	Imports ExecTransportError and docker_errors; moves raise stream.run_loop_exception inside the try so stored exceptions are covered; adds a gated except (ExecTransportError, docker_errors.NotFound) clause with exc_info=True logging.
strix/interface/tui/app.py	Calls coordinator.mark_shutting_down() at the top of _fire_sandbox_cleanup() so the flag is set before sandbox containers are killed.

_{Reviews (3): Last reviewed commit: "Gate sandbox-error swallow on coordinato..." | Re-trigger Greptile}