feat(runtime): add Bevy 0.20 live editor M0 spike

- new bevy_forge_runtime crate with EditorPlugin, EditorState, Selection
- native Bevy UI shell + official bevy_ui_widgets 0.20 (no egui in runtime)
- live hierarchy, reflection inspector, translate gizmo, editor camera
- deterministic 1440x900/1000x640 screenshot mode
- demo example, docs and screenshots; v1 crates untouched
- interactive computer-use test fixed inspector command-queue panic

README.md

@@ -24,6 +24,20 @@ the output easy to review, diff and check in.
 Live in-game editing (a Bevy plugin with a remote protocol) is a roadmap item, not part of this
 editor.
 
+## v2 live editor (M0 spike)
+
+The `v2-live-editor` branch moves editing into the game as a **Bevy 0.20 plugin** with native Bevy
+UI and official `bevy_ui_widgets` — no egui in the runtime crate. M0 ships the `EditorPlugin`, a
+fixed editor shell, live hierarchy, reflection inspector, translate gizmo, editor camera and
+deterministic screenshots at 1440×900 / 1000×640.
+
+```bash
+cargo run -p bevy_forge_runtime --example editor_spike
+```
+
+See [docs/m0-spike.md](docs/m0-spike.md) for controls, architecture and M0 limits. The v1 standalone
+editor below remains the current released workflow.
+
 ## Two viewports
 
 | 2D scene editing | 3D wireframe preview |