feat(voice): add sidecar Whisper ears

[CompleteDotTech]

Summary

• adds browser PCM capture, client-side endpointing, and session-numbered partial/final events for the local whisper.cpp adapter
• adds the loopback Whisper route, using a verified downloaded GGML model and a configured whisper-cli runtime
• prefers ready sidecar Whisper ears ahead of native macOS STT and shows the honest local-Whisper call label

Closes #3804

Verification

• pnpm typecheck
• focused voice/API test command (40 passing)
• pnpm test:app reached an existing CRLF-sensitive assertion in src-tauri/release-runtime.test.mjs after 74 passing files
• pnpm lint could not run eslint because the shared dependency cache does not contain its executable

Tracking

• Bead cave-vkah could not be claimed or updated: bd is not installed on this machine. The linked GitHub issue and this PR provide the handoff record.