feat(headless): headless server runtime for LiveAgent

[thirsty5034]

Summary

Add a headless runtime for LiveAgent: the same business command surface the desktop build exposes via #[tauri::command] runs as a standalone axum HTTP/WebSocket server (--no-default-features, no Tauri), serving the existing WebUI through an in-page bridge.

Scope (P1)

• Decouple the business layer from Tauri (event emission, State/macro, AppContext)
• Headless binary with axum server + command dispatch; same-interface tauriBridge for the WebUI
• Reproducible command-registry/generator pipeline for the 234-command adapter layer
• Same-origin security model (CORS gate, token auth, WS origin check, real-peer rate limiting)
• Layered dev-tools Docker images (core/full) with mise-managed runtimes

Deliverable

PR: feat(headless): headless server runtime, manifest-driven command adapters, security hardening, and dev-tools Docker images