Give street props colliders, zoned placements and variants

Props were decoration: the guard and guests walked straight through benches,
bins, bollards and planters. They now block movement and steer guests around.

Collision
- _add_prop_model() fits a StaticBody3D from the model's mesh bounds in
  holder-local space: a cylinder for bollard/bin/hydrant, a box otherwise, so
  placement rotation and variant scale carry over.
- Fallback primitives go through the same fit, so a missing .glb cannot silently
  remove collision.
- Each prop also publishes a NavigationObstacle3D; NpcAvatar enables agent
  avoidance and moves with the safe velocity from velocity_computed. The navmesh
  stays a flat walkable plane and avoidance does the steering.

Placement
- PROP_PLACEMENTS groups furniture by entrance, mid-block and curb zones, with a
  static placement_problems() validator for bounds, overlap/min-spacing,
  duplicates, and the door/steps/guest-lane exclusions.
- variant_for(index) gives deterministic yaw jitter, subtle scale, and optional
  clutter (bag by the bin, crate by the newspaper boxes, cone by the hydrant).

Verification
- New windowed smoke_props.gd: guard walks into a bench and stops; a guest
  headed beyond the bench routes around it and never enters the collider.
- Headless 182 -> 187: placement validation and its failure modes, variant
  determinism/range, collider + obstacle on every placed prop, fallback collider.
- Other smokes (PLAN verbs, crowd, emergency, timeline) still pass; Python
  tooling 53/53; screenshots recaptured; compare 9 good / 0 bad.
- Version 0.4.0. TODO: collision/placement section moved to DONE; prop pipeline
  checks remain.

src/test/smoke_props.gd

@@ -0,0 +1,165 @@
+extends SceneTree
+## Prop-collision smoke: proves the guard and an NPC cannot walk through street
+## furniture, and that a guest slides around a bench instead of passing through
+## it. Windowed (the guard reads captured-mouse input):
+##
+##   godot --path . --script res://src/test/smoke_props.gd
+##
+## Exit code 0 = pass, 1 = failure.
+
+const MAX_FRAMES := 1800
+const GUARD_PUSH_FRAMES := 100
+
+var frame := 0
+var gm: Node = null
+var started := false
+var step := 0
+var step_frame := 0
+var failures: Array[String] = []
+var bench: Node3D = null
+var bench_center := Vector3.ZERO
+var bench_body: StaticBody3D = null
+var guard_start := Vector3.ZERO
+var npc: Node3D = null
+var npc_start := Vector3.ZERO
+
+func _initialize() -> void:
+	root.size = Vector2i(1280, 720)
+	root.add_child(load("res://scenes/main.tscn").instantiate())
+
+func _process(_delta: float) -> bool:
+	frame += 1
+	if gm == null:
+		gm = root.find_child("GameManager", true, false)
+		return false
+	if not started:
+		gm.call("_on_venue_selected", "hollywood_building")
+		Input.set_mouse_mode(Input.MOUSE_MODE_CAPTURED)
+		started = true
+		return false
+	if frame > MAX_FRAMES:
+		_fail("timeout before the collision checks finished")
+		return true
+	step_frame += 1
+	match step:
+		0:
+			_find_bench()
+			if bench == null:
+				return false
+			# Stand a couple of metres in front of the bench and walk into it.
+			var start := bench_center + Vector3(0, 0, 2.2)
+			start.y = 0.1
+			gm.guard.global_position = start
+			# Face the bench (-z): with the guard's basis, forward input at yaw PI
+			# walks toward lower z.
+			gm.guard.rotation.y = PI
+			guard_start = start
+			Input.action_press("move_forward")
+			step = 1
+			step_frame = 0
+		1:
+			if step_frame >= GUARD_PUSH_FRAMES:
+				Input.action_release("move_forward")
+				_check(guard_start.z - gm.guard.global_position.z > 0.5,
+					"guard walked toward the bench")
+				_check(gm.guard.global_position.z > bench_center.z + 0.25,
+					"guard stopped at the bench instead of passing through it")
+				_check(not _inside_bench(gm.guard.global_position),
+					"guard is not inside the bench collider")
+				# Step the guard aside so the guest test hits the bench, not the player.
+				gm.guard.global_position = bench_center + Vector3(4.0, -0.08, 2.2)
+				_stage_npc()
+				step = 2
+				step_frame = 0
+		2:
+			if step_frame % 120 == 0 and npc != null and is_instance_valid(npc):
+				print("npc dbg pos=%s vel=%s arrived=%s wait=%s" % [str(npc.global_position), str(npc.velocity), str(npc.arrived), str(npc.awaiting_interaction)])
+			if npc == null or not is_instance_valid(npc):
+				_stage_npc()
+				return false
+			if _npc_finished():
+				_check(npc.global_position.z < bench_center.z - 0.4,
+					"guest reached the far side of the bench")
+				_check(not _inside_bench(npc.global_position),
+					"guest is not inside the bench collider")
+				_check(npc_start.distance_to(npc.global_position) > 1.0,
+					"guest moved while routing around the prop")
+				_finish()
+				return true
+	return false
+
+func _find_bench() -> void:
+	var detail := gm.get_node_or_null("World/StreetDetail")
+	if detail == null:
+		# The world root name differs between scene builds; search instead.
+		detail = root.find_child("StreetDetail", true, false)
+	if detail == null:
+		_fail("StreetDetail not found")
+		return
+	for child in detail.get_children():
+		if str(child.name).begins_with("Prop_bench"):
+			bench = child as Node3D
+			break
+	if bench == null:
+		_fail("no bench prop placed")
+		return
+	bench_center = bench.global_position
+	bench_body = bench.get_node_or_null("Collision") as StaticBody3D
+	if bench_body == null:
+		_fail("bench has no static collider")
+
+func _stage_npc() -> void:
+	if gm.npcs.is_empty():
+		step = 0
+		step_frame = 0
+		return
+	npc = gm.npcs[0]
+	npc_start = bench_center + Vector3(0, 0.5, 2.5)
+	npc.global_position = npc_start
+	npc.velocity = Vector3.ZERO
+	npc.arrived = false
+	npc.awaiting_interaction = false
+	npc.lifetime_s = 999.0
+	npc.reaction_mode = ""
+	# Target well past the bench forces a straight line through it, and stays
+	# beyond the controller's 3 m "arrived" shortcut so the guest must route.
+	npc.target_position = Vector3(bench_center.x, 0.5, bench_center.z - 5.0)
+
+func _npc_finished() -> bool:
+	if npc == null or not is_instance_valid(npc):
+		return false
+	return npc.global_position.z < bench_center.z - 0.4 \
+		or npc.global_position.distance_to(npc.target_position) < 0.9
+
+func _inside_bench(point: Vector3) -> bool:
+	if bench_body == null:
+		return false
+	var collider := bench_body.get_node_or_null("Shape") as CollisionShape3D
+	if collider == null or not (collider.shape is BoxShape3D):
+		return false
+	var box := collider.shape as BoxShape3D
+	var half := box.size * 0.5
+	var center := collider.global_position
+	half.x += 0.1
+	half.z += 0.1
+	return absf(point.x - center.x) < half.x and absf(point.z - center.z) < half.z
+
+func _check(condition: bool, message: String) -> void:
+	if condition:
+		print("ok: " + message)
+	else:
+		_fail(message)
+
+func _fail(message: String) -> void:
+	failures.append(message)
+	_finish()
+
+func _finish() -> void:
+	Input.action_release("move_forward")
+	if failures.is_empty():
+		print("SMOKE OK: props block the guard and guests route around them")
+		quit(0)
+	else:
+		for message in failures:
+			printerr("SMOKE FAIL: " + message)
+		quit(1)

src/test/tests/test_generated_props.gd

@@ -83,6 +83,96 @@ func test_world_places_generated_props() -> bool:
 	root.free()
 	return a and b and c and d
 
+func test_prop_placements_are_valid() -> bool:
+	var problems := WorldBuilder.placement_problems()
+	return TestUtils.check(problems.is_empty(),
+		"prop placements keep the door, steps and approach lane clear (%s)" % str(problems))
+
+func test_placement_validator_catches_problems() -> bool:
+	var bad: Array = WorldBuilder.PROP_PLACEMENTS.duplicate(true)
+	bad.append({"zone": "test", "prop": "bench", "x": 0.0, "z": 2.0})
+	bad.append({"zone": "test", "prop": "bench", "x": 0.0, "z": 2.0})
+	var problems := WorldBuilder.placement_problems(bad)
+	var a := TestUtils.check(not problems.is_empty(), "validator rejects bad placements")
+	var joined := " ".join(problems)
+	var b := TestUtils.check(joined.contains("steps and door"),
+		"validator reports the door/steps exclusion")
+	var c := TestUtils.check(joined.contains("duplicate"), "validator reports a duplicate")
+	return a and b and c
+
+func test_prop_variants_are_deterministic() -> bool:
+	var first := WorldBuilder.variant_for(3, 180.0)
+	var second := WorldBuilder.variant_for(3, 180.0)
+	var other := WorldBuilder.variant_for(4, 180.0)
+	var a := TestUtils.check(is_equal_approx(first["rotation"], second["rotation"])
+		and is_equal_approx(first["scale"], second["scale"]),
+		"the same placement always gets the same variant")
+	var b := TestUtils.check(not is_equal_approx(first["rotation"], other["rotation"]),
+		"different placements get different rotations")
+	var c := TestUtils.check(first["scale"] >= 0.95 and first["scale"] <= 1.05,
+		"variant scale stays subtle")
+	var d := TestUtils.check(absf(first["rotation"] - 180.0) <= 2.01,
+		"variant rotation stays near the authored angle")
+	return a and b and c and d
+
+func test_every_prop_has_a_collider() -> bool:
+	var root := Node3D.new()
+	var builder := WorldBuilder.new(root)
+	builder.build()
+	var detail := root.get_node_or_null("StreetDetail")
+	var problems: Array[String] = []
+	if detail == null:
+		problems.append("no StreetDetail")
+	else:
+		for holder in detail.get_children():
+			var body := holder.get_node_or_null("Collision")
+			if body == null or not (body is StaticBody3D):
+				problems.append("%s has no StaticBody3D" % holder.name)
+				continue
+			var collider := body.get_node_or_null("Shape") as CollisionShape3D
+			if collider == null or collider.shape == null:
+				problems.append("%s has no collision shape" % holder.name)
+				continue
+			var size: Vector3
+			if collider.shape is BoxShape3D:
+				size = (collider.shape as BoxShape3D).size
+			elif collider.shape is CylinderShape3D:
+				var cylinder := collider.shape as CylinderShape3D
+				size = Vector3(cylinder.radius * 2.0, cylinder.height, cylinder.radius * 2.0)
+			else:
+				problems.append("%s uses an unexpected shape" % holder.name)
+				continue
+			if size.x <= 0.05 or size.y <= 0.05 or size.z <= 0.05:
+				problems.append("%s has a degenerate collider" % holder.name)
+			if collider.position.y + size.y * 0.5 <= 0.05:
+				problems.append("%s collider sits below the ground" % holder.name)
+			if holder.get_node_or_null("Avoidance") == null:
+				problems.append("%s has no navigation obstacle" % holder.name)
+	root.free()
+	return TestUtils.check(problems.is_empty(), "every prop has a static collider (%s)" % str(problems))
+
+func test_fallback_props_get_the_same_collider() -> bool:
+	## A missing `.glb` must not silently remove collision: fallback primitives go
+	## through the same bounds fit as the imported models.
+	var root := Node3D.new()
+	var builder := WorldBuilder.new(root)
+	var holder := Node3D.new()
+	var fallback := builder._fallback_prop("bench")
+	holder.add_child(fallback)
+	builder._add_prop_collision(holder, "bench", fallback)
+	var body := holder.get_node_or_null("Collision") as StaticBody3D
+	var a := TestUtils.check(body != null, "fallback bench gets a static body")
+	var collider := body.get_node_or_null("Shape") as CollisionShape3D if body else null
+	var b := TestUtils.check(collider != null and collider.shape is BoxShape3D,
+		"fallback bench gets a box shape")
+	var width: float = (collider.shape as BoxShape3D).size.x if b else 0.0
+	var c := TestUtils.check(width > 1.0, "fallback collider follows the bench width (%.2f)" % width)
+	var d := TestUtils.check(holder.get_node_or_null("Avoidance") is NavigationObstacle3D,
+		"fallback bench publishes a navigation obstacle")
+	holder.free()
+	root.free()
+	return a and b and c and d
+
 func test_world_facade_windows_light_at_night() -> bool:
 	var root := Node3D.new()
 	var builder := WorldBuilder.new(root)