fix(daemon): stop the remote browser on SIGTERM

[yangshu2087]

Problem

The daemon only handled SIGINT (KeyboardInterrupt). On SIGTERM the process was terminated before the finally block ran, so stop_remote() never fired and the remote browser leaked (and kept billing).

This path is hit in practice:

• admin.py escalates to os.kill(pid, signal.SIGTERM) when the graceful "shutdown" IPC can't be delivered (hung/unreachable daemon).
• Container runtimes (Docker/k8s) send SIGTERM on stop.

Fix

Register an asyncio SIGTERM handler that sets the existing stop Event — the same graceful path as the "shutdown" command — so main() unwinds cleanly and the finally block runs stop_remote().

• Registered before start(), because get_ws_url() / the CDP handshake can take seconds and a signal during that window must still trigger cleanup. The stop Event is moved to __init__ so it exists in time.
• POSIX-only: add_signal_handler raises NotImplementedError on Windows, where SIGTERM can't be caught anyway — guarded.

Test

Adds test_main_registers_sigterm_handler_that_triggers_graceful_stop: asserts main() registers the handler (via the public loop.remove_signal_handler, which returns True iff one was set) and that setting the stop Event drives a graceful return. No real signal is delivered (a regression would otherwise kill the test runner). Skipped on Windows.

Full suite: 115 passed.

🤖 Generated with Claude Code

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Summary by cubic

Ensure the daemon stops the remote browser on SIGTERM to avoid leaks and surprise billing. A SIGTERM now triggers the same graceful shutdown path so stop_remote() always runs.

• Bug Fixes
  • Add asyncio SIGTERM handler (POSIX-only) that sets the stop event; register it before start().
  • Create the stop event in init so signals during startup are honored.
  • Add a unit test that verifies the handler is registered and main() exits gracefully (skipped on Windows).

^{Written for commit cfd7e18. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}