Add voice dictation / microphone input for external ACP agents

[shadow-identity]

Check for existing issues

• Completed

Describe the feature

Please add voice dictation / microphone input to the Agent Panel for external ACP agents, especially Codex.

Today, Codex desktop supports dictation, but Zed's Agent Panel does not expose any mic / push-to-talk flow for Codex via ACP. ACP already defines audio content blocks and an audio prompt capability, so Zed should be able to surface this when the selected agent supports it.

This would make external agents much more practical for prompt dictation and quick follow-up instructions.

Related:

• OpenAI Codex IDE extension request: Voice transcription for IDE extension openai/codex#3000
• ACP audio content support: https://agentclientprotocol.com/protocol/content

If applicable, add mockups / screenshots to help present your vision of the feature

No mockup.

[yeskunall]

Hey @shadow-identity -- feature requests go through discussions.

[yeskunall]

Related:

• Dictation for Assistant (inline and chat-based) #16410
• Agent speech to text dictation feature #52393