feat(gemini & rime): implemented close() for google and rime tts

[KrishnaShuk]

Description

This PR implements robust cleanup logic for the Gemini and Rime TTS plugins by adding an AbortController and a close() method.

Tracking issue #881

Changes Made

• Added an AbortController and close() method to the TTS class .

Pre-Review Checklist

• Build passes: All builds (lint, typecheck, tests) pass locally
• AI-generated code reviewed: Removed unnecessary comments and ensured code quality
• Changes explained: All changes are properly documented and justified above
• Scope appropriate: All changes relate to the PR title, or explanations provided for why they're included
• Video demo: A small video demo showing changes works as expected and did not break any existing functionality using Agent Playground (if applicable)

Testing

• Automated tests added/updated (if applicable)
• All tests pass
• Make sure both restaurant_agent.ts and realtime_agent.ts work properly (for major changes)

Additional Notes

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Note to reviewers: Please ensure the pre-review checklist is completed before starting your review.

[changeset-bot]

🦋 Changeset detected

Latest commit: 9473d49

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

This PR includes changesets to release 2 packages

Name	Type
@livekit/agents-plugin-google	Patch
@livekit/agents-plugin-rime	Patch

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