Installer: Integrate lemond binary and model management UI

[kovtcharov-amd]

Summary

Lemonade recently shipped lemond, a standalone binary designed for embedding into third-party applications. This issue tracks the deeper integration path: replacing the full Lemonade MSI with lemond and building a model management dashboard in Agent UI.

This is the follow-up to #774 (bundle Lemonade MSI — easy path in v0.17.3).

Scope

1. Replace Lemonade MSI with lemond

• Bundle lemond binary directly instead of the full Lemonade MSI installer
• Manage lemond lifecycle from GAIA (start, stop, health check)
• Smaller footprint and tighter control vs. full MSI install

2. Model Management Dashboard in Agent UI

• Build a model management view in Agent UI (src/gaia/apps/webui/)
• Capabilities:
  • Browse available models
  • Download / delete models
  • Switch active model
  • Show download progress
  • Display model metadata (size, quantization, context length)
• Backend: new router in src/gaia/ui/routers/ to proxy lemond model operations

3. Lifecycle integration

• GAIA starts/stops lemond as a managed subprocess
• Health checks and auto-restart
• Version gating aligned with LEMONADE_VERSION in src/gaia/version.py

Related issues

• Installer: Bundle Lemonade Server into GAIA installer #774 — Bundle Lemonade MSI into GAIA installer (v0.17.3, easy path)
• Pre-configured distribution package #711 — Pre-configured distribution package
• Installer: Silent and Unattended Install Mode #614 — Installer: Silent and Unattended Install Mode
• Update Lemonade installer and version gating for v10 (DEB naming, Linux NPU) #533 — Update Lemonade installer and version gating for v10