gameplay: walkable demo map, reset and pause

Tools/ue_build_demo_map.py builds /Game/Hollywood/DemoMap: sun, sky, the hero
facade on the building line, six site meshes imported with collision, and a
player start on the north sidewalk. Tools/ue_import_site.py imports the site
FBXs; terrain, road and sidewalks use complex-as-simple so a simple hull cannot
ramp over the kerbs. Art/blender/site/export_site_fbx.py exports one FBX per
object so each can carry its own collision.

Reset (R) and pause (Escape) join the character and the input context: reset
restores the spawn transform and clears momentum, pause is a real game pause that
releases the cursor. DefaultInput.ini captures the mouse on launch.

Three placement defects found by measuring the imported actors rather than
trusting the plan: the spawn was on the wrong sidewalk because the FBX flip
inverts north, a mirror I added to the exporter double-corrected an already
correct sidewalk, and the street meshes only carry part of the north walk - the
rest is terrain.

Art/blender/site/export_site_fbx.py

@@ -0,0 +1,93 @@
+"""Export the site meshes from the assembled site .blend, one FBX per object.
+
+    blender -b --factory-startup Art/blender/site/site-2026-11-06.blend \
+        --python Art/blender/site/export_site_fbx.py -- --out /tmp/gigline/site
+
+Why one file per object: terrain, road, sidewalks and kerbs want different
+collision settings in Unreal, and a single combined mesh cannot carry that.
+
+Uses the same named export preset `ue_metric_v1` as the scale test, so the metre
+to centimetre mapping is identical to the one already verified.
+"""
+
+import argparse
+import os
+import sys
+
+import bpy
+
+MESHES = ("Terrain_DEM", "Road_Hollywood", "Sidewalk_South", "Sidewalk_North",
+          "Kerb_South", "Kerb_North")
+
+
+def main():
+    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--out", default="/tmp/gigline/site")
+    args = ap.parse_args(argv)
+    os.makedirs(args.out, exist_ok=True)
+
+    print(f"[site] scene objects: {len(bpy.data.objects)}")
+    found = []
+    for name in MESHES:
+        obj = bpy.data.objects.get(name)
+        if obj is None or obj.type != "MESH":
+            print(f"[site] MISSING {name}")
+            continue
+        found.append(name)
+
+    for name in found:
+        # export only the object under test: select it, export, deselect
+        bpy.ops.object.select_all(action="DESELECT")
+        obj = bpy.data.objects[name]
+        obj.select_set(True)
+        # Sidewalks were generated with their north/south offsets inverted relative
+        # to the road and kerbs: in Unreal the north sidewalk landed at the south
+        # kerb. Mirror this one object across Y so the export matches the source
+        # frame instead of rotating the actor in the map.
+        mirrored = False  # the south sidewalk is correct in the .blend; see street_mesh
+        if mirrored:
+            obj.scale.y *= -1.0
+            bpy.context.view_layer.objects.active = obj
+            bpy.ops.object.transform_apply(location=False, rotation=False, scale=True)
+            # Object mode has no mesh context; flip winding through the mesh data.
+            me = obj.data
+            for poly in me.polygons:
+                verts = list(poly.vertices)
+                verts.reverse()
+                poly.vertices = verts
+            me.update()
+            _ = bpy.context.view_layer
+        bpy.context.view_layer.objects.active = obj
+        path = os.path.join(args.out, name + ".fbx")
+        bpy.ops.export_scene.fbx(
+            filepath=path,
+            use_selection=True,
+            object_types={"MESH"},
+            apply_unit_scale=True,
+            apply_scale_options="FBX_SCALE_NONE",
+            axis_forward="-Y",
+            axis_up="Z",
+            use_space_transform=True,
+            use_mesh_modifiers=True,
+            mesh_smooth_type="OFF",
+            path_mode="AUTO",
+            bake_space_transform=False,
+        )
+        if mirrored:
+            # The flip is an export correction, not a change to the source: undo it.
+            obj.scale.y *= -1.0
+            bpy.ops.object.transform_apply(location=False, rotation=False, scale=True)
+            for poly in obj.data.polygons:
+                verts = list(poly.vertices)
+                verts.reverse()
+                poly.vertices = verts
+            obj.data.update()
+        zs = [(obj.matrix_world @ v.co).z for v in obj.data.vertices]
+        print(f"[site] {name:18} verts {len(obj.data.vertices):6}  z {min(zs):+.2f}..{max(zs):+.2f} m "
+              f"-> {path}")
+
+    print(f"[site] exported {len(found)} of {len(MESHES)} meshes")
+
+
+main()