fix: #175 BidiStream SIGTERM causes CPU hot loop and pod stuck in Terminating

[brightsparc]

fixes: #175

When a pod receives SIGTERM during an active BidiStream invocation, two bugs caused the worker to spin at ~82% CPU and never exit:

1. ReceiveChannel.__call__() blocked forever on an empty queue after the disconnect event was consumed
2. create_poll_or_cancel_coroutine() fed empty body frames (b'') to the VM, creating a tight loop with no useful await points

Changes

• server_types.py: Return synthetic http.disconnect when queue is drained and channel is disconnected
• server_context.py: Skip notify_input() for empty body frames; add 30s timeout to block_until_http_input_closed() in leave()
• tests/disconnect_hotloop.py: Regression tests for both fixes

[github-actions]

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[brightsparc]

I have read the CLA Document and I hereby sign the CLA

[tillrohrmann]

Thanks a lot for creating this fix @brightsparc. cc @igalshilman for review.

[brightsparc]

Thanks a lot for creating this fix @brightsparc. cc @igalshilman for review.

Cool, looking forward to getting this landed to reduce the hot loop when draining pods.

[igalshilman]

That's a good one!

[igalshilman]

looks good! Thank you @brightsparc

[igalshilman]

note to self: run verification tests once the docker image is built.