Maps are editor-built scenes: [Tool] Playground/Crag, headless rebuild for agents

scenes/maps/playground.tscn and crag.tscn are generated by the map scripts' Rebuild (inspector
button, or godot-mono --headless --path . tools/rebuild_maps.tscn) and loaded as saved by the game,
so hand edits stick. The crag route is saved as Marker3D nodes and crag_spike checks the saved
scene. Layout verified identical to the code-built one (tools/map_dump.tscn).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/Playground.cs

@@ -1,7 +1,9 @@
 using Godot;
 using System.Collections.Generic;
 
-// The body-physics sandbox (Nimso-sandbox style), built in code around the spawn/table area:
+// The body-physics sandbox (Nimso-sandbox style) around the spawn/table area. EDITOR-BUILT: this is the
+// root of scenes/maps/playground.tscn and Rebuild() generates the pieces below into that scene
+// (MapScene: inspector button, or tools/rebuild_maps.tscn headless); the game loads the saved scene.
 //   EAST  — mantling ledges (0.3 … 1.5 m), a 1 m platform with stairs, a walkable 18° ramp and a
 //           too-steep 40° one, a climbing wall with holds onto a 2.4 m top, a pull-up bar, monkey bars.
 //   WEST  — physics toys: a plank bridge on two blocks (walk on it / knock it off), loose planks,
@@ -10,8 +12,12 @@ using System.Collections.Generic;
 //   SOUTH — a crawl tunnel (0.6 m clearance), a duck-under bar (1.2 m) and a doorway.
 // Static pieces are world (layer 1) and grabbable for climbing (PropGrabber grabs any static body
 // not in "no_grab"); dynamic pieces are "prop"s (grab/push) and come back with Reset().
+[Tool]
 public partial class Playground : Node3D
 {
+    [ExportToolButton("Rebuild (replaces all children)")]
+    public Callable RebuildButton => Callable.From(RebuildInEditor);
+
     private readonly List<(RigidBody3D Body, Transform3D Start)> _dynamic = new();
     private const uint WorldLayer = 1, WorldMask = 0b11101, PropMask = 0b11101;
 
@@ -21,22 +27,28 @@ public partial class Playground : Node3D
 
     public override void _Ready()
     {
+        if (!Engine.IsEditorHint())
+            MapScene.CollectProps(this, _dynamic);
+    }
+
+    public void Reset() => MapScene.Reset(_dynamic);
+
+    private void RebuildInEditor()
+    {
+        if (!MapScene.CanRebuildInEditor(this))
+            return;
+        Rebuild();
+        MapScene.MarkUnsaved();
+    }
+
+    // Replaces every child with the generated layout, owned by this map (saved with its scene).
+    public void Rebuild()
+    {
+        MapScene.Clear(this);
         BuildEast();
         BuildWest();
         BuildSouth();
-    }
-
-    public void Reset()
-    {
-        foreach (var (body, start) in _dynamic)
-        {
-            if (!IsInstanceValid(body))
-                continue;
-            body.GlobalTransform = start;
-            body.LinearVelocity = Vector3.Zero;
-            body.AngularVelocity = Vector3.Zero;
-            body.ResetPhysicsInterpolation();
-        }
+        MapScene.Adopt(this);
     }
 
     // ---------------------------------------------------------------- builders
@@ -46,7 +58,7 @@ public partial class Playground : Node3D
         StaticBody3D body = new() { Name = name, CollisionLayer = WorldLayer, CollisionMask = WorldMask, Transform = new Transform3D(basis ?? Basis.Identity, center) };
         body.AddChild(new CollisionShape3D { Shape = new BoxShape3D { Size = size } });
         body.AddChild(Mesh(new BoxMesh { Size = size }, color));
-        AddChild(body);
+        AddChild(body, true);
         return body;
     }
 
@@ -59,7 +71,7 @@ public partial class Playground : Node3D
         StaticBody3D body = new() { Name = name, CollisionLayer = WorldLayer, CollisionMask = WorldMask, Transform = new Transform3D(new Basis(x, y, x.Cross(y)), (from + to) * 0.5f) };
         body.AddChild(new CollisionShape3D { Shape = new CylinderShape3D { Radius = radius, Height = len } });
         body.AddChild(Mesh(new CylinderMesh { TopRadius = radius, BottomRadius = radius, Height = len, RadialSegments = 12 }, color));
-        AddChild(body);
+        AddChild(body, true);
         return body;
     }
 
@@ -75,11 +87,10 @@ public partial class Playground : Node3D
             MaxContactsReported = 4,
             PhysicsMaterialOverride = new PhysicsMaterial { Friction = friction, Bounce = 0.05f },
         };
-        body.AddToGroup("prop");
+        body.AddToGroup(MapScene.PropGroup, true);
         body.AddChild(new CollisionShape3D { Shape = shape });
         body.AddChild(Mesh(mesh, color));
-        AddChild(body);
-        _dynamic.Add((body, body.GlobalTransform));
+        AddChild(body, true);
         return body;
     }
 
@@ -97,13 +108,14 @@ public partial class Playground : Node3D
     {
         AddChild(new Label3D
         {
+            Name = "Sign",
             Text = text,
             FontSize = 96,
             PixelSize = 0.002f,
             OutlineSize = 12,
             Billboard = BaseMaterial3D.BillboardModeEnum.FixedY,
             Position = at,
-        });
+        }, true);
     }
 
     // ---------------------------------------------------------------- zones
@@ -183,13 +195,16 @@ public partial class Playground : Node3D
         // Seesaw: a plank hinged on a pivot block.
         Block("SeesawPivot", new Vector3(0.3f, 0.45f, 0.5f), new Vector3(-8.5f, 0.225f, -1.5f), Metal);
         RigidBody3D seesaw = BoxProp("Seesaw", new Vector3(3.2f, 0.06f, 0.45f), 12f, new Vector3(-8.5f, 0.48f, -1.5f), DarkWood);
+        // Joint paths resolve relative to the joint (a sibling here) and are saved that way; set
+        // before AddChild so the joint never exists without its bodies.
         HingeJoint3D pivot = new()
         {
+            Name = "SeesawHinge",
             Transform = new Transform3D(new Basis(Vector3.Right, Vector3.Up, Vector3.Back), new Vector3(-8.5f, 0.48f, -1.5f)),
-            NodeA = GetNode<Node>("SeesawPivot").GetPath(),   // absolute: joint paths resolve relative to the joint
-            NodeB = seesaw.GetPath(),
+            NodeA = $"../{GetNode<Node>("SeesawPivot").Name}",
+            NodeB = $"../{seesaw.Name}",
         };
-        AddChild(pivot);
+        AddChild(pivot, true);
         Sign("Seesaw", new Vector3(-8.5f, 1.3f, -1.5f));
 
         // Swing board: a 10 kg board hinged at its top edge from a 2.4 m beam — grab it and hang.
@@ -199,11 +214,12 @@ public partial class Playground : Node3D
         RigidBody3D board = BoxProp("SwingBoard", new Vector3(1.2f, 1.2f, 0.05f), 10f, new Vector3(-6f, 1.75f, 1.5f), Wood);
         HingeJoint3D swing = new()
         {
+            Name = "SwingHinge",
             Transform = new Transform3D(new Basis(Vector3.Back, Vector3.Up, Vector3.Left), new Vector3(-6f, 2.35f, 1.5f)),
-            NodeA = beam.GetPath(),
-            NodeB = board.GetPath(),
+            NodeA = $"../{beam.Name}",
+            NodeB = $"../{board.Name}",
         };
-        AddChild(swing);
+        AddChild(swing, true);
         Sign("Hanging board", new Vector3(-6f, 2.9f, 1.5f));
 
         // Crate pyramid (4 kg each), a heavy 25 kg box, barrels.