fix: avoid retrying aborted LLM requests during shutdown

[tobiplancraft]

Summary

• treat already-aborted inference LLM streams as expected cancellation after request creation
• return early for aborted streams in the error path so shutdown does not reclassify cancellation as a retryable API failure
• prevent noisy retry logs when a participant disconnect aborts an in-flight goodbye generation

Test plan

• Reproduce the bug locally with a modified manual_shutdown.ts end-call flow
• Build @livekit/agents
• Verify the fix removes retry spam for aborted LLM requests during session shutdown

Fixes #1245

[changeset-bot]

🦋 Changeset detected

Latest commit: 3575d25

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 24 packages

Name	Type
@livekit/agents	Patch
@livekit/agents-plugin-anam	Patch
@livekit/agents-plugin-assemblyai	Patch
@livekit/agents-plugin-baseten	Patch
@livekit/agents-plugin-bey	Patch
@livekit/agents-plugin-cartesia	Patch
@livekit/agents-plugin-deepgram	Patch
@livekit/agents-plugin-elevenlabs	Patch
@livekit/agents-plugin-google	Patch
@livekit/agents-plugin-hedra	Patch
@livekit/agents-plugin-inworld	Patch
@livekit/agents-plugin-lemonslice	Patch
@livekit/agents-plugin-livekit	Patch
@livekit/agents-plugin-mistral	Patch
@livekit/agents-plugin-neuphonic	Patch
@livekit/agents-plugin-openai	Patch
@livekit/agents-plugin-phonic	Patch
@livekit/agents-plugin-resemble	Patch
@livekit/agents-plugin-rime	Patch
@livekit/agents-plugin-sarvam	Patch
@livekit/agents-plugin-silero	Patch
@livekit/agents-plugins-test	Patch
@livekit/agents-plugin-trugen	Patch
@livekit/agents-plugin-xai	Patch

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[CLAassistant]

All committers have signed the CLA.

[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.