Implement filler word filter with bonus features

[raaghs01]

Core Implementation:

• Add FillerFilter class for detecting filler-only speech
• Integrate with agent_activity interrupt logic
• Support environment variable (IGNORED_FILLER_WORDS) and code configuration
• Add confidence threshold filtering (default 0.5)
• Implement detailed logging ([IGNORED_FILLER], [VALID_INTERRUPT])
• Thread-safe async operations with asyncio.Lock()

Bonus Feature #1 - Dynamic Updates via REST API:

• REST API server for runtime filler word updates
• POST /update_filler endpoint (add/remove words)
• GET /fillers endpoint (query current configuration)
• Zero-downtime configuration changes
• Thread-safe concurrent request handling

Bonus Feature #2 - Multi-Language Support:

• Support for 10 languages (en, hi, es, fr, de, ja, zh, pt, it, ko)
• Automatic language switching based on STT metadata
• Manual language switching capability
• Custom language addition support
• Language-specific filler databases

Testing:

• 10 core implementation tests (all passing)
• 10 standalone verification tests (all passing)
• 21 bonus feature tests (all passing)
• Total: 41/41 tests passed (100%)

Documentation:

• FILLER_FILTER_README.md (600+ lines)
• IMPLEMENTATION_SUMMARY.md (300+ lines)
• BONUS_FEATURES.md (400+ lines)
• FINAL_SUBMISSION.md (500+ lines)
• QUICK_REFERENCE.md (300+ lines)

Files Added:

• livekit-agents/livekit/agents/voice/filler_filter.py (500+ lines)
• livekit-agents/livekit/agents/voice/filler_api.py (230+ lines)
• test_filler_filter.py (350+ lines)
• test_standalone.py (300+ lines)
• test_bonus_features.py (400+ lines)
• examples/filler_filter_example.py
• examples/filler_api_example.py

Files Modified:

• livekit-agents/livekit/agents/voice/agent_activity.py
• livekit-agents/livekit/agents/voice/agent_session.py

Author: Raghav
Assessment: LiveKit Intern - Filler Filter Implementation

[CLAassistant]

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[raaghs01]

CI Check Status

I've signed the CLA. Regarding the failing checks:

Ruff Check Failure

The Ruff errors are in pre-existing LiveKit code, not in my changes:

[Dark-Sys-Jenkins]

Hi reaching out on behalf of Salescode.ai team please do not raise PR against livekit repo. We have your application, do not re open the PR. Thanks for understanding.