fix: don't swallow _ExitCli during shutdown

[lawrence3699]

Closes #4664

What was happening

_ExitCli is raised from the CLI signal handlers to stop the worker. Because it inherited from Exception, broad except Exception blocks could catch it before the shutdown path reached drain() / aclose().

SupervisedProc._memory_monitor_task() is one concrete path: if SIGTERM lands while psutil.Process(...) is running, the task logs and swallows _ExitCli instead of letting the worker drain.

What changed

• make _ExitCli inherit from BaseException
• add a regression test covering _memory_monitor_task()

Why this is correct

_ExitCli is internal control flow used only for process shutdown, and the CLI already catches it explicitly at the top level. Making it bypass generic except Exception handlers lets shutdown propagate without changing the existing explicit _ExitCli handling.

Validation

• uv run pytest tests/test_drain_timeout.py -q
• uv run ruff check livekit-agents/livekit/agents/cli/cli.py tests/test_drain_timeout.py

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[devin-ai-integration]

✅ Devin Review: No Issues Found

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

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[Copilot]

Pull request overview

This PR fixes a shutdown control-flow issue where _ExitCli (raised by CLI signal handlers) could be accidentally caught by broad except Exception blocks, preventing the normal drain/close shutdown path from running.

Changes:

• Change _ExitCli to inherit from BaseException so it bypasses generic except Exception handlers.
• Add a regression test ensuring SupervisedProc._memory_monitor_task() does not log/swallow _ExitCli.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
livekit-agents/livekit/agents/cli/cli.py	Makes _ExitCli a BaseException to ensure shutdown signals aren’t intercepted by broad exception handling.
tests/test_drain_timeout.py	Adds a regression test covering the _memory_monitor_task() path to ensure _ExitCli propagates and isn’t logged/swallowed.

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[longcw]

thanks for the pr!

[longcw]

could you sign the CLA before we can merge?