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

crates/bevy_forge_runtime/examples/editor_live.rs

@@ -0,0 +1,30 @@
+//! M1 live editor: the editor plugin on top of `DefaultPlugins`, loading a real
+//! `.forge.ron` scene selected through the environment.
+//!
+//! Run the garden demo from the repository root:
+//!
+//! ```text
+//! FORGE_PROJECT=examples/demo-project \
+//! FORGE_SCENE=scenes/garden.forge.ron \
+//! cargo run -p bevy_forge_runtime --example editor_live
+//! ```
+//!
+//! `FORGE_SCENE=""` disables scene loading. With no scene (or a load failure)
+//! the editor still starts with its placeholder camera and empty hierarchy.
+
+use bevy::{prelude::*, window::WindowResolution};
+use bevy_forge_runtime::EditorPlugin;
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins.set(WindowPlugin {
+            primary_window: Some(Window {
+                title: "Bevy Forge — M1 Core".into(),
+                resolution: WindowResolution::new(1440, 900).with_scale_factor_override(1.0),
+                ..default()
+            }),
+            ..default()
+        }))
+        .add_plugins(EditorPlugin)
+        .run();
+}