Update conversation subclasses to use emit

[kraenhansen]

Summary

• Replace this.options.onAudio, this.options.onAudioAlignment, and this.options.onError in VoiceConversation with this.emit() calls
• Remove no-op callback defaults from getFullOptions — the emitter handles the no-listeners case naturally
• Keep pre-instance callbacks (onStatusChange, onConnect, etc.) as direct fullOptions.onXxx() calls since errors during startSession must propagate to the caller

Part of #738 (PR 5/6).

Test plan

• All 97 client tests pass (including "preserves the original startup error when cleanup throws")
• All 32 turbo tasks pass (build, check-types, lint across all packages)
• Pre-instance callbacks still fire correctly during startSession

🤖 Generated with Claude Code

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Note

Medium Risk
Changes how VoiceConversation surfaces audio/alignment/error notifications (now via emit instead of direct option callbacks) and removes default no-op callbacks, which could affect consumers that relied on those option handlers being invoked implicitly.

Overview
Updates VoiceConversation to emit audio, audio-alignment, and error events instead of calling options.onAudio, options.onAudioAlignment, and options.onError directly.

Removes the no-op default callback assignments from BaseConversation.getFullOptions, relying on the emitter’s no-listener behavior rather than pre-populating option handlers.

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