Add Realtime Voice plugin

[NoHara42]

Summary

Adds realtime_voice to the Agent Zero Plugin Index: continuous, interruptible speech-to-speech conversation using OpenAI's Realtime API, alongside the existing voice mode.

The Realtime model handles conversation, not agent work. A single delegate_to_agent function hands tasks to the normal Agent Zero agent, gives a short spoken acknowledgement while it works, and speaks the result when it returns.

• Source and setup
• Release 0.1.1 and installable ZIP
• Security model and data handling

Integration

• Direct browser-to-OpenAI WebRTC audio; no third-party voice hosting. Session setup runs through Agent Zero and the OpenAI API key stays server-side.
• Reuses Agent Zero's API key storage, scoped plugin settings, and normal chat/task path. Delegated work follows the agent's existing model and tool configuration.
• UI controls for starting/stopping calls, mute, interruption, and captions, with theme-aware settings. Existing voice mode remains available.

Validation

• 42 Python tests and 11 JavaScript tests passed, covering session setup, delegation, input/error handling, and conversation state.
• Live Chromium testing with synthetic microphone audio covered WebRTC, actual terminal delegation, spoken results, and barge-in. Install, enable/disable, and uninstall were exercised in an isolated instance.
• Authentication and CSRF checks passed for all three backend endpoints; dark/light UI styling was checked.
• The official submission validator passed against the published repository and generated index; this PR's validate CI check also passed.

Scope and limitations

This PR adds only plugins/realtime_voice/index.yaml; runtime code stays in the source repository.

The plugin inherits Agent Zero's trusted-instance security model and agent permissions. Audio and conversation data are sent to OpenAI, and usage is billable. Ending a call does not cancel agent work already started. Safari/mobile and remote reverse-proxy deployments have not been verified; setup, manual test steps, and known limitations are documented in the README.

[POWERFULMOVES]

Verified: index-only addition, validate CI green. Upstream repo https://github.com/NoHara42/a0-realtime-voice reachable (HTTP 200). Tags/labels consistent with catalog. Safe index entry.