feat: add USER_SPEECH_STARTED and USER_SPEECH_ENDED events

[bc-anam]

Summary

• Adds USER_SPEECH_STARTED and USER_SPEECH_ENDED to DataChannelMessage enum (wire values: userSpeechStarted, userSpeechEnded)
• Adds matching AnamEvent enum values and EventCallbacks type signatures
• Handles new messages in StreamingClient.setupDataChannels() onmessage switch — emits public events directly with correlationId

These events fire when the engine's VAD detects user speech start/end, before transcription is available. Clients can use them for "listening" indicators and similar UX.

The callback receives a correlationId: string that matches the eventual MESSAGE_STREAM_EVENT_RECEIVED event's correlation ID.

Companion PRs: anam-engine#2520 (engine + WebRTC), docs (event documentation)

Test plan

• Verify USER_SPEECH_STARTED fires when user begins speaking (before transcript)
• Verify USER_SPEECH_ENDED fires when user stops speaking
• Verify correlationId matches between speech events and subsequent transcript
• Verify no errors for sessions that don't emit these events (audio passthrough, LiveKit)

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Summary by cubic

Add early VAD-driven user speech start/end events so apps can show “listening” UI before transcription. Each event includes a correlationId that matches the later transcript event.

• New Features

  • Added userSpeechStarted and userSpeechEnded to DataChannelMessage.
  • Added USER_SPEECH_STARTED and USER_SPEECH_ENDED to AnamEvent and EventCallbacks (correlationId: string).
  • StreamingClient emits these events on data-channel messages using user_action_correlation_id.

• Bug Fixes

  • Aligned public event enums and callback types with internal data-channel messages to prevent type mismatches.

^{Written for commit 7be3013. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 4 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/types/events/public/EventCallbacks.ts">

<violation number="1" location="src/types/events/public/EventCallbacks.ts:51">
P2: These callbacks are typed as always receiving a string, but the emitter can pass `undefined` via `message.data?.user_action_correlation_id`.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}