feat(runtime): add M1 scene persistence, undo/redo and hotkeys

- load .forge.ron through bevy_forge_core into the live ECS (3D components)
- Ctrl+S syncs and saves the document; custom components are preserved
- transform undo/redo for inspector sliders and gizmo drags (Ctrl+Z/Y)
- F focus, Delete subtree, Ctrl+D duplicate; camera subtrees are guarded
- 66 runtime tests; workspace 412 passed; garden demo docs/screenshots

README.md

@@ -38,6 +38,20 @@ 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.
 
+### M1 Core — real scene load/save + undo
+
+M1 loads a real `.forge.ron` scene through `bevy_forge_core`, saves edits with Ctrl+S, adds
+Transform undo/redo (Ctrl+Z / Ctrl+Shift+Z / Ctrl+Y) and the F focus, Delete and Ctrl+D duplicate
+hotkeys.
+
+```bash
+FORGE_PROJECT=examples/demo-project \
+FORGE_SCENE=scenes/garden.forge.ron \
+cargo run -p bevy_forge_runtime --example editor_live
+```
+
+See [docs/m1-core.md](docs/m1-core.md) for the garden demo, hotkeys and M1 limits.
+
 ## Two viewports
 
 | 2D scene editing | 3D wireframe preview |