[Feature] Speaker Gate: 'My Voice Only' Verification Filter

[SentimentalK]

1. Goal

Speaker Gate using Sherpa-ONNX speaker verification to ensure Echolet only transcribes primary user voice.

2. Architecture

• Voice profile enrollment (~/.echolet/profile/voice_profile.bin).
• Segment embedding extraction & cosine similarity threshold check.
• Scope: Speaker Gate / Verification (not simultaneous source separation).