Show the extractor derrick the moment it is built, not on respawn

Follow-up to #9: the marker was resolved once in Planet._ready() on the
assumption that extractors are built on PlanetSurface.tscn, so a Planet
node could never outlive a change to its own answer. That assumption was
wrong. Extractors are built from SPACE, via
BuildController._planet_under_fleet() with the fleet parked on the
planet, so the Planet node is already in the tree with _ready() long
since run. The derrick therefore did not appear until the planet
happened to despawn and respawn - building one read as doing nothing.

GameState now emits extractor_added, and Planet keeps its marker in step
with it, redrawing only when its own answer actually changes.

The test missed this because it spawned a fresh planet after registering
the extractor, which is not the order the game does it in. It now keeps
a planet alive across the build and asserts the derrick appears on that
node.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

GameState.gd

@@ -270,12 +270,20 @@ func has_extractor_at(planet_name: String) -> bool:
 	return false
 
 
+signal extractor_added(planet_name: String)
+
+
 func add_extractor(planet_name: String, at_position: Vector2) -> void:
 	extractors.append({
 		"position": at_position,
 		"planet_name": planet_name,
 		"progress": 0.0,
 	})
+	# An extractor is built from SPACE, with the fleet parked on the planet -
+	# so the Planet node is already in the tree with its _ready() long since
+	# run. Without this it kept showing no derrick until it happened to
+	# despawn and respawn, which reads as the build having done nothing.
+	extractor_added.emit(planet_name)
 
 
 func get_hauler_route_time(extractor: Dictionary) -> float:

Planet.gd

@@ -29,9 +29,12 @@ const EXTRACTOR_MARKER_COLOR: Color = Color(1.0, 0.85, 0.3)
 const DERRICK_HEIGHT: float = 44.0
 const DERRICK_HALF_WIDTH: float = 16.0
 
-# Resolved once in _ready() rather than polled: building an extractor happens
-# on PlanetSurface.tscn, and coming back to space rebuilds Main.tscn from
-# scratch, so a Planet node never outlives a change to its own answer.
+# Kept in step with GameState.extractor_added rather than polled per frame.
+# An extractor is built from SPACE (BuildController._planet_under_fleet(),
+# with the fleet parked on the planet), so this node is already in the tree
+# with its _ready() long since run when the answer changes - resolving it
+# only at _ready() left the planet looking untouched until it happened to
+# despawn and respawn.
 var shows_extractor: bool = false
 
 
@@ -47,6 +50,16 @@ func _ready() -> void:
 		var radius: float = rng.randf_range(70.0, 100.0)
 		shape_points.append(Vector2(cos(angle), sin(angle)) * radius)
 	shows_extractor = GameState.has_extractor_at(planet_name)
+	GameState.extractor_added.connect(_on_extractor_added)
+	queue_redraw()
+
+
+func _on_extractor_added(built_on: String) -> void:
+	# Only the planet it was actually built on, and only a redraw when the
+	# answer really changed - every other planet in range gets this too.
+	if built_on != planet_name or shows_extractor:
+		return
+	shows_extractor = true
 	queue_redraw()
 
 

tests/test_planet_extractor_marker.gd

@@ -29,6 +29,7 @@ var map_content: Node2D
 var planet_chunk: Vector2i
 var planet_name: String = ""
 var stage: int = 0
+var already_spawned: Node2D
 
 
 func _initialize() -> void:
@@ -78,13 +79,29 @@ func _process(_delta: float) -> bool:
 				print("TEST_PLANET_EXTRACTOR_MARKER: FAIL (map badge with no extractor)")
 				quit(1)
 				return true
-			clean.queue_free()
 			print("no extractor -> no derrick, no badge (planet '%s')" % planet_name)
 
+			# Deliberately keep this planet ALIVE across the build. An
+			# extractor is built from space with the fleet parked on the
+			# planet (BuildController._planet_under_fleet()), so the node is
+			# already in the tree with _ready() long since run. Resolving the
+			# marker only at _ready() meant the planet kept looking untouched
+			# until it happened to despawn and respawn - the build read as
+			# having done nothing at all. Spawning a fresh planet afterwards
+			# (as the checks below do) cannot catch that.
+			already_spawned = clean
 			game_state.add_extractor(planet_name, WorldGen.chunk_origin(planet_chunk))
 			stage = 1
 			return false
 		1:
+			# --- the planet that was already on screen when it was built --
+			if not already_spawned.shows_extractor:
+				print("TEST_PLANET_EXTRACTOR_MARKER: FAIL (a planet already in the tree never picked up its derrick - the build reads as doing nothing)")
+				quit(1)
+				return true
+			print("planet already in the tree picked up its derrick on build")
+			already_spawned.queue_free()
+
 			# --- extractor built ----------------------------------------
 			var mined: Node2D = _spawn_planet()
 			if not mined.shows_extractor: