Integrate Kenney Starter Kit FPS assets + comprehensive test suite

Assets (CC0 license):
- 3D models: Blaster gun, walls, platforms, grass, clouds, enemy
- Sounds: blaster fire, impacts, footsteps, jumps, weapon change
- Sprites: crosshair, hit marker, muzzle flash, skybox, blob shadow
- Font: Lilita One

Code changes:
- weapon_manager.gd: load blaster.glb as gun model (replaces box mesh)
- player.tscn: use Kenney sounds (blaster.ogg, enemy_hurt/destroy) and crosshair

Test suite (100 unit tests + 4 integration scenarios):
- weapon_data.gd: 27 tests — all 6 weapons every stat verified
- economy.gd: 19 tests — constants, loss streak, buy thresholds
- bomb.gd: 15 tests — state machine, timing constants
- round_manager.gd: 10 tests — win conditions, elimination logic
- team_manager.gd: 8 tests — auto-balance, team assignment
- headless_test_bot.gd: integration bot with movement/idle/rounds scenarios
- run_multi_bot.sh: multi-client launcher

assets/kenney-fps/objects/enemy.gd

@@ -0,0 +1,68 @@
+extends Node3D
+
+@export var player: Node3D
+
+@onready var raycast = $RayCast
+@onready var muzzle_a = $MuzzleA
+@onready var muzzle_b = $MuzzleB
+
+var health := 100
+var time := 0.0
+var target_position: Vector3
+var destroyed := false
+
+# When ready, save the initial position
+
+func _ready():
+	target_position = position
+
+
+func _process(delta):
+	self.look_at(player.position + Vector3(0, 0.5, 0), Vector3.UP, true)  # Look at player
+	target_position.y += (cos(time * 5) * 1) * delta  # Sine movement (up and down)
+
+	time += delta
+
+	position = target_position
+
+# Take damage from player
+
+func damage(amount):
+	Audio.play("sounds/enemy_hurt.ogg")
+
+	health -= amount
+
+	if health <= 0 and !destroyed:
+		destroy()
+
+# Destroy the enemy when out of health
+
+func destroy():
+	Audio.play("sounds/enemy_destroy.ogg")
+
+	destroyed = true
+	queue_free()
+
+# Shoot when timer hits 0
+
+func _on_timer_timeout():
+	raycast.force_raycast_update()
+
+	if raycast.is_colliding():
+		var collider = raycast.get_collider()
+
+		if collider.has_method("damage"):  # Raycast collides with player
+			
+			# Play muzzle flash animation(s)
+
+			muzzle_a.frame = 0
+			muzzle_a.play("default")
+			muzzle_a.rotation_degrees.z = randf_range(-45, 45)
+
+			muzzle_b.frame = 0
+			muzzle_b.play("default")
+			muzzle_b.rotation_degrees.z = randf_range(-45, 45)
+
+			Audio.play("sounds/enemy_attack.ogg")
+
+			collider.damage(5)  # Apply damage to player