Describe persistent Variables assets and clearing saved data (#166)

Architecture.md

@@ -80,6 +80,7 @@ src/core/graph/        graph model, NodeRegistry/NodeContext/values (a travellin
                        narrows one down to what a PropertyBag may hold, #157), interpreter, dropTarget, nested (behaviors as nodes),
                        emitGraph (the walk both graph compilers share: each node once, in dependency order; cycles and property names reported),
                        sharedState (what a run shares: a bag per Variables asset, the state of a global machine),
+                       savedValues (#166: the SaveArea a run reads persistent Variables assets from and writes them to, and restoring a save through today's declaration),
                        stateMachine (the State node, a machine's states, the ports they become), variablePorts, propertyPorts,
                        lookup (what a node may look up: behaviors, state machines), keyRepeat; nodes/{events,flow,data,action,variable}/<Name>.ts
 src/core/particles/    nodes (the catalogue), compile (a graph → one function per output),

Behaviors.md

@@ -207,6 +207,16 @@ shown on the node and editable in the inspector.
   next run starts from. Two Variables assets may declare the same name without meeting: the
   asset is the key, not the name. A coin counter is one such asset with `coins` in it; picking a
   coin up is one node, `coins` fed through `Add` back into itself.
+- **Saved values (savegame)**: tick **Persistent** in a Variables asset's inspector and its values
+  outlive the run — a highscore, the levels unlocked, the player's settings. The next Play starts
+  where the last one ended instead of at the declared values. Nothing new is needed in the graph:
+  the same `Variables` nodes read and write them, and every change is saved as it happens, so a
+  closed tab loses nothing. The save lives in **this browser**, per project, and never in the
+  project file. Played and editor runs save apart, so trying a behavior with *Run in editor* does
+  not touch the player's save. To test a first start again, **Clear saved values** under the switch
+  forgets that asset, and **Menu → Clear saved data** forgets the whole project. A save is read
+  through the declaration as it is now: a variable deleted since is dropped, one added since starts
+  at its declared value, and a value whose kind changed is converted like any other value.
 - **Cross-object state** the other way: a behavior's own variables *are* the properties of its
   object, so another graph reads and writes them with `Object by name` → `Properties` of type
   *Behavior*. That reaches one named object, where a Variables asset belongs to no object at all.

Concepts.md

@@ -14,7 +14,7 @@
 | **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 stores the container object **and nothing else** — its content is resolved from the template on every read, so a template edit reaches every instance at once. **Create container** turns the current selection into such an asset: the selected objects move into the template and the scene keeps one placed container at their centre (world positions unchanged). The template is edited in the **Container** tab (see [Containers](Containers)) or from an instance through **Apply to container**. |
 | **Selection** | One or more scene objects. Click selects, `Ctrl`/`Shift`-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** 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. |
-| **Variables asset** | Declarations and nothing else — no graph, no position, never placed. A `Variables` node naming it reads and writes **one value per key for the whole run**, however many graphs point at it. The values start at the declared ones on every Play and are never written back, so playing cannot change the project; while a run is on the asset's inspector shows them live and an edit there reaches the run at once. Two such assets may declare the same name without meeting. See [Behaviors](Behaviors). |
+| **Variables asset** | Declarations and nothing else — no graph, no position, never placed. A `Variables` node naming it reads and writes **one value per key for the whole run**, however many graphs point at it. The values start at the declared ones on every Play and are never written back, so playing cannot change the project; while a run is on the asset's inspector shows them live and an edit there reaches the run at once. Two such assets may declare the same name without meeting. A **Persistent** one keeps its values past the end of the run, in this browser: the next Play starts where the last one ended — the savegame. See [Behaviors](Behaviors). |
 | **Run in editor** | A switch only behaviors have (default off). With it on the behavior keeps running while the project is **not** playing — and unlike Play it then edits the *saved* model: what it moves or writes is a real change, autosaved and not on the undo stack. See *Running without Play*. |
 | **Run while paused** | The other switch only behaviors have (default off). While a graph has paused the game (`Pause game`), only behaviors with it on are ticked — the pause menu, which is also the only thing that can resume. See *The game pauses itself*. |
 | **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. |

Development.md

@@ -13,7 +13,7 @@ npm run check        # typecheck + lint + format:check + tests, the gate CI runs
 npm run build        # writes dist/ and regenerates index.html
 ./build.sh           # the same under `set -o pipefail`, for callers that pipe the output
 php tools/make-user.php <name> <password>                     # an account; every tool signs in (see Accounts)
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1272 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1278 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result