Apply/revert buttons for overrides, container instances and child positions

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -12,12 +12,13 @@ Live: <https://nockal.com/game-maker/> · Widget playground: <https://nockal.com
 |---|---|
 | **Asset** | Named thing with a type (`scene`, `camera`, `sprite`, `behavior`, `collider`, `container`) and typed properties. Assets have **no position**. |
 | **Scene object** | An asset placed into a scene: a link to the asset + a **position** (`x`, `y`, `z`) + sparse **overrides** of the asset's properties + an optional **parent** (another object of the scene). Scenes cannot be placed. |
-| **Container** | A reusable group ("prefab"): the asset holds a **template** of objects (asset link, local position, overrides, parent links) centred on its origin. Placing a container creates a container object plus fresh copies of the template below it – ordinary objects, each remembering its template id. **Create container** turns the current selection into such an asset and replaces the selected objects by one placed container at their centre (world positions unchanged). Editing the template itself comes later. |
+| **Container** | A reusable group ("prefab"): the asset holds a **template** of objects (asset link, local position, overrides, parent links) centred on its origin. Placing a container creates a container object plus fresh copies of the template below it – ordinary objects, each remembering its template id. **Create container** turns the current selection into such an asset and replaces the selected objects by one placed container at their centre (world positions unchanged). The template is edited from its instances (see *Instance*). |
 | **Selection** | One or more scene objects. Click selects, `Ctrl`-click adds/removes, dragging on empty scene space draws a rubber band (objects whose position lies inside are selected). Dragging a selected object moves the whole selection; `Delete` removes it; the inspector offers **Create container** and **Remove from scene** for several objects. |
 | **Behavior** | Logic as an asset: a **node graph** plus the **variables** it declares. Placed like anything else (a diamond symbol in the scene); its parent is the **owner** the graph acts on. |
 | **Collider** | A shape (box or circle) for collision detection, placed as a **child** of the object it belongs to (its *body*). Drawn as a green outline in edit mode only. |
-| **Override** | A per-object value that replaces the asset's value for one property. Only changed keys are stored; the inspector marks them bold and offers a reset (↺). |
+| **Override** | A per-object value that replaces the asset's value for one property. Only changed keys are stored; the inspector marks them bold and offers a reset (↺) and an **apply** (↑) that writes the value into the asset instead. |
 | **Default** | Every property has a schema default. Asset values that differ from it are marked bold in the inspector and can be reset (↺) the same way an override can. |
+| **Instance** | An object that is part of a placed container. Its base is the **template**, not just the asset: position and overrides that differ from the template are bold, ↺ reverts to the template, ↑ ▾ offers **Apply to container** (template; copies still at the old value follow, copies changed on their own keep theirs) or **Apply to asset**. Position rows apply to the container directly. |
 | **Edit mode** | The Scene tab draws the project model; panels, grid, gizmos and drag-to-move are active. |
 | **Play mode** | The editor switches to a **runtime copy** of the project (same ids). A `World` is instantiated from its active scene (one entity per scene object, resolved properties as mutable state) and shown in the **Game** tab. Systems tick it and mirror their changes into the copy; every panel stays open and edits the copy, which the world picks up immediately. **Stop discards world and copy** – the saved model is never touched. |
 
@@ -198,5 +199,5 @@ object in the selection (hierarchy rows too).
 
 ## Not yet
 
-Textures on sprites, editing a container's template (changes reaching all instances),
-reordering the hierarchy, auth, touch-optimised layout, graph comments/groups.
+Textures on sprites, editing a container's template directly (today changes reach it only
+via **Apply to container** from an instance), reordering the hierarchy, auth, touch-optimised layout, graph comments/groups.