Add crowd presentation, fix NPC navigation, refresh screenshots

NPC navigation (previously dead in the live game)
- Only assign NavigationAgent3D.target_position when it changes: re-assigning every
  frame invalidated the path, so get_next_path_position() kept returning the current
  point and avatars never moved.
- Follow the first path point that is closer to the destination than the avatars are.
  Nav points sit on the navmesh plane (y=0) while bodies stand at y~0.5, so the old
  3D distance test always looked "already there"; path[0] is also the old start point,
  so a naive "far enough away" pick steered backwards and oscillated.
- Fix fsm.state -> fsm.current_state in the idle-lifetime check.

Crowd presentation
- Aggressive behavior, visible weapons, and responder arrivals make idle bystanders
  stop and face the incident for 12 s; someone waiting at the entrance keeps focus.
- Panic (mood >= 0.75) walks people away from the door at 2.4 m/s, then they despawn.
- Wire reactions to EventBus.crowd_changed: CrowdSystem.apply_event() emits on the bus,
  not on its own `changed` signal (the first wiring received nothing).
- Measured a 16-NPC entrance at ~1.2 ms/frame (824 fps, vsync off), so no LOD/culling.

World and HUD
- Skyline is now a ring of four alpha-scissored planes at 200 m instead of a single
  plane; PlaneMesh defaults to horizontal, which is why the backdrop rendered as a band
  overhead. Larger ground plane, mipmapped texture, scissor threshold 0.5 (0.3 left
  mip dashes in the sky), lifted albedo so the city is not pure black.
- Flashlight aims straight ahead and lights the person/door instead of the ground.
- Shorter HUD controls line so it stops overlapping itself.

Tests, tooling, docs
- Headless suite 98 -> 105 (new test_crowd_presentation.gd, 7 tests).
- New smoke_crowd.gd: rubbernecking, panic, and flee-target sanity.
- capture_screenshots.gd starts a shift from the venue menu and stages the night set
  properly; all six README screenshots regenerated.
- README, TODO/DONE (crowd section moved), MEMORY updated. Version 0.2.4.

src/game/world_builder.gd

@@ -57,9 +57,11 @@ func _add_box(parent: Node3D, size: Vector3, pos: Vector3, color: Color, cast_sh
 func _build_ground() -> void:
 	var ground := StaticBody3D.new()
 	ground.name = "Ground"
-	_add_box(root, Vector3(160, 0.5, 160), Vector3(0, -0.25, 20), Color(0.22, 0.24, 0.26))
+	# Large enough that the ground meets the distant skyline ring (no gap of sky
+	# under the buildings when looking down the boulevard).
+	_add_box(root, Vector3(500, 0.5, 500), Vector3(0, -0.25, 20), Color(0.22, 0.24, 0.26))
 	var col := BoxShape3D.new()
-	col.size = Vector3(160, 1, 160)
+	col.size = Vector3(500, 1, 500)
 	var shape_owner := ground.create_shape_owner(ground)
 	ground.shape_owner_add_shape(shape_owner, col)
 	root.add_child(ground)
@@ -165,29 +167,49 @@ func _build_navmesh() -> void:
 	root.add_child(region)
 
 func _build_skyline_backdrop() -> void:
-	## Skyline silhouette backdrop behind the building. The texture has a
-	## transparent sky, so only the building silhouettes show; the material must
-	## be set up for alpha or the plane renders as an opaque slab (ADR/TODO).
+	## Distant skyline surrounding the block. The texture's sky is transparent
+	## (alpha scissor), so only building silhouettes show. Four planes form a
+	## ring: a single plane placed behind the building reads as a floating black
+	## band from the sidewalk.
 	var backdrop := Node3D.new()
 	backdrop.name = "SkylineBackdrop"
-	var plane := MeshInstance3D.new()
-	var mesh := PlaneMesh.new()
-	mesh.size = Vector2(240, 60)  # wide, low horizon
-	plane.mesh = mesh
 	var mat := StandardMaterial3D.new()
 	mat.albedo_texture = T_SKYLINE
 	mat.texture_repeat = true
-	mat.uv1_scale = Vector3(2.0, 1.0, 1.0)
+	mat.uv1_scale = Vector3(3.0, 1.0, 1.0)
 	mat.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA_SCISSOR
-	mat.alpha_scissor_threshold = 0.3
+	mat.alpha_scissor_threshold = 0.5
 	mat.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
 	mat.cull_mode = BaseMaterial3D.CULL_DISABLED
-	plane.material_override = mat
-	plane.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
-	plane.position = Vector3(0, 18, -60)  # behind and above the building
-	backdrop.add_child(plane)
-	root.add_child(backdrop)
+	# Unshaded silhouettes read as pure black at 255-scale; lift the albedo so the
+	# distant skyline sits closer to a hazy daytime city.
+	mat.albedo_color = Color(2.6, 2.7, 3.0, 1.0)
 	_skyline_mat = mat
+	var mesh := PlaneMesh.new()
+	# PlaneMesh defaults to a horizontal (XZ) plane; the skyline must stand up.
+	mesh.orientation = PlaneMesh.FACE_Z
+	mesh.size = Vector2(400, 60)
+	# Far enough that the skyline reads as background and its top edge stays out
+	# of the middle of the sky.
+	const DIST := 200.0
+	# The texture keeps its buildings in the lower part of the image, so the plane
+	# center sits at half its height: the building bases meet the ground.
+	const CENTER_Y := 30.0
+	var placements := [
+		[Vector3(0, CENTER_Y, -DIST), 0.0],
+		[Vector3(0, CENTER_Y, DIST), 0.0],
+		[Vector3(-DIST, CENTER_Y, 0), PI / 2.0],
+		[Vector3(DIST, CENTER_Y, 0), PI / 2.0],
+	]
+	for placement in placements:
+		var plane := MeshInstance3D.new()
+		plane.mesh = mesh
+		plane.material_override = mat
+		plane.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
+		plane.position = placement[0]
+		plane.rotation.y = placement[1]
+		backdrop.add_child(plane)
+	root.add_child(backdrop)
 
 var _skyline_mat: StandardMaterial3D = null