Add standoff sniper enemy (#45)

EnemyStandoffComponent holds a preferred distance from the nearest
player ship instead of ramming (advance beyond it, retreat inside
retreat_range_factor of it, drift laterally in the comfortable band
between) - never paired with a pursuit component. EnemyRangedWeaponComponent
mirrors VesselWeaponComponent for an enemy: fires an EnemyProjectile
aimed at the target's CURRENT position rather than led, so a moving
ship can dodge it (projectile_speed 260 vs the interceptor's 460
max_speed). Registered in EnemyDefinitions so it's placeable from a
planet setup by enemy_id.

test_sniper_enemy.gd went through a few iterations to get its own
timing right: physics ticks can run ahead of a SceneTree test's own
_process() clock under this device's load, so the cooldown-violation
check reads the component's own fire_timer directly (a rising value
means it refired) instead of comparing projectile counts against a
wall-clock wait, and manually repositioned ships need their
move_target re-pinned or Ship's own steering silently drives them back
to the stale target.

Part of the #40 conquest-mechanic breakdown.

EnemyRangedWeaponComponent.gd

@@ -0,0 +1,54 @@
+class_name EnemyRangedWeaponComponent
+extends Node
+
+# Same shape as VesselWeaponComponent, mirrored for an enemy: fires an
+# EnemyProjectile at the nearest player ship's CURRENT position, not led,
+# so a moving ship can dodge it.
+
+var capability_id: String = "ranged_weapon"
+
+@export var fire_range: float = 700.0
+@export var fire_cooldown: float = 2.2
+@export var projectile_speed: float = 260.0
+@export var damage: int = 1
+
+var fire_timer: float = 0.0
+var projectile_scene: PackedScene = preload("res://EnemyProjectile.tscn")
+
+
+func tick(delta: float) -> void:
+	fire_timer -= delta
+	if fire_timer > 0.0:
+		return
+	var enemy: Node2D = get_parent()
+	var target: Node2D = _nearest_ship_in_range(enemy)
+	if target == null:
+		fire_timer = 0.25
+		return
+	var projectile: Area2D = projectile_scene.instantiate()
+	# global_position: the projectile is reparented to root, a different
+	# node than the enemy's own (possibly nested) parent, so local
+	# position would be wrong the moment an enemy isn't a direct root
+	# child - exactly the case #44 introduced (planet-surface hosting).
+	projectile.position = enemy.global_position
+	projectile.damage = damage
+	projectile.speed = projectile_speed
+	enemy.get_tree().root.add_child(projectile)
+	projectile.launch(target.global_position - enemy.global_position)
+	fire_timer = fire_cooldown
+
+
+func _nearest_ship_in_range(enemy: Node2D) -> Node2D:
+	var fleet: Node2D = get_tree().get_first_node_in_group("player_fleet")
+	if fleet == null:
+		return null
+	var nearest: Node2D = null
+	var best_distance: float = fire_range
+	for ship in fleet.ships:
+		if not is_instance_valid(ship):
+			continue
+		var distance: float = enemy.global_position.distance_to(ship.global_position)
+		if distance <= best_distance:
+			best_distance = distance
+			nearest = ship
+	return nearest