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>

tools/map_dump.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://tools/MapDump.cs" id="1"]
+
+[node name="MapDump" type="Node3D"]
+script = ExtResource("1")