Build the WinUI 3 QuickJS host app

[nakasyou]

Summary

Build the WinUI 3 host app that embeds QuickJS, implements the renderer ABI, and boots a compiled Eclipsa native app in development and test modes.

Done when

• A WinUI 3 host can run the native bundle, route events into QuickJS, and participate in the common dev workflow including HMR.

Depended issues

• Embed QuickJS runtime abstractions in native-core #78
• Implement native HMR transport and patch protocol #82
• Bring file-route parity to the native runtime #85
• Run loaders on native route navigation #86
• Create the @eclipsa/native-winui3 binding package #93