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.

Tools/ue_create_input_assets.py

@@ -118,11 +118,21 @@ def build():
     ia_left.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
     save(ia_left)
 
+    # Reset and pause are boolean: one press, no accumulator.
+    ia_reset = fresh("IA_Reset", unreal.InputAction, unreal.InputAction_Factory)
+    ia_reset.set_editor_property("value_type", unreal.InputActionValueType.BOOLEAN)
+    save(ia_reset)
+
+    ia_pause = fresh("IA_Pause", unreal.InputAction, unreal.InputAction_Factory)
+    ia_pause.set_editor_property("value_type", unreal.InputActionValueType.BOOLEAN)
+    save(ia_pause)
+
     mapping_table = [
         (ia_move, "W"), (ia_back, "S"), (ia_strafe, "D"), (ia_left, "A"),
         (ia_move, "Gamepad_LeftY"), (ia_strafe, "Gamepad_LeftX"),
         (ia_look, "MouseX"), (ia_look, "MouseY"), (ia_look, "Gamepad_Right2D"),
         (ia_jump, "SpaceBar"), (ia_jump, "Gamepad_FaceButton_Bottom"),
+        (ia_reset, "R"), (ia_pause, "Escape"),
     ]
 
     mappings = []