Implemented interrupt to consider stt

[namanjain2005]

feat(voice): add state-aware backchannel handler to prevent false interruptions

Summary

This commit introduces a dedicated BackchannelHandler to correctly handle passive user acknowledgements during real-time voice interactions. The refactor ensures the agent can distinguish between false interruptions and true interruptions without modifying the low-level VAD system.

Key Changes

• Extracted backchannel detection and state handling into BackchannelHandler
• Ignored passive acknowledgements (e.g., yeah, ok, hmm, uh-huh) only when the agent is speaking
• Allowed the same short utterances to be treated as valid conversational input when the agent is silent
• Implemented built-in exit command detection (exit, quit, stop, bye, goodbye, end)
• Skipped backchannel transcripts from the session transcript buffer

Behavior Guarantees

• No pauses or stutters on filler words while the agent is speaking
• Immediate interruption on explicit stop commands
• Existing false-interrupt grace window preserved
• No VAD kernel changes (agent-layer only)

Notes

• Backchannel ignore list is configurable
• Designed to remain low-latency and real-time safe
• Code is modular and easy to extend

Demo

**Demo video:**https://drive.google.com/file/d/1JDimL3FRVnkRxb8ToilZx4sE3KDvhjJV/view