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.

Game/GigLine/Config/DefaultGame.ini

@@ -7,3 +7,9 @@ CopyrightNotice=
 BuildConfiguration=PPBC_Development
 FullRebuild=False
 UsePakFile=True
+
+[/Script/EngineSettings.GameMapsSettings]
+; Temporary default while the demo map is being built; GameMapsSettings in
+; DefaultEngine.ini still names the game mode only.
+GameDefaultMap=/Game/Test/ReviewMap
+EditorStartupMap=/Game/Test/ReviewMap