Transport Hub building

Forgejo #18, part 5 of #12. The building only - the vessels that do the
hauling are #19. Placeable, costed at 30, gated behind a new "Freight
Handling" research node hanging off Logistics, with its own info popup,
build-menu glyph and map marker.

Drawn as an octagonal dock ring with berth arms and a squared-off freight
core: deliberately radial-but-flat so it does not read as a small
mothership, which is the only structure with swept arms. Its stationed
transports are NeonPiece children of one rotating holder, per #10 - the
geometry is rasterised once and only the holder's rotation changes, so
the traffic costs no redraws.

Building._draw()'s match has a catch-all that renders anything
unrecognised as a ship crafter, so a missing case is silent and looks
almost right. The test checks for the hub's own _hub_traffic holder
rather than trusting that something plausible appeared - which caught
exactly that: a _ready() patch had silently not applied and the hub was
rendering through the crafter branch.

The build menu grew a third row. Every button, label and price moved:
the old row occupied 332px against a 372px pitch, and three of those do
not fit above a 1280px screen. Rows are now shorter (128px buttons, 40px
price digits) at a 290px pitch, ending at y=1176. Rendered and looked at
- the first attempt tightened the pitch alone and left every price
overlapping the row beneath it, which no headless test would have seen.

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

Building.gd

@@ -28,6 +28,19 @@ extends Node2D
 const MOTHERSHIP_COLOR: Color = Color(0.45, 0.9, 0.55)
 const CRAFTER_COLOR: Color = Color(1.0, 0.72, 0.25)
 const COMMAND_COLOR: Color = Color(0.55, 0.6, 1.0)
+const TRANSPORT_HUB_COLOR: Color = Color(0.95, 0.55, 0.85)
+
+# Transport hub: an octagonal dock ring with berths around it and a freight
+# core in the middle. Deliberately radial-but-flat, so it does not read as a
+# small mothership - the mothership is the only thing with swept arms.
+const HUB_RING_RADIUS: float = 74.0
+const HUB_DECK_RADIUS: float = 54.0
+const HUB_CORE_RADIUS: float = 22.0
+const HUB_BERTH_COUNT: int = 8
+const HUB_BERTH_LENGTH: float = 20.0
+const HUB_DOCKED_COUNT: int = 3
+const HUB_DOCKED_ORBIT: float = 96.0
+const HUB_SPIN_SPEED: float = 0.22
 # The vessel on the assembly line is drawn in the fleet's own colour, so it
 # reads as "one of yours being built" rather than as shipyard machinery.
 const HULL_COLOR: Color = Color(0.25, 0.85, 1.0)
@@ -85,6 +98,8 @@ var _hoist: NeonPiece = null
 var _sparks: Node2D = null
 var _hull_holder: Node2D = null
 var _hull_pieces: Array = []
+# Rotating holder for the transports stationed at a transport hub (#18).
+var _hub_traffic: Node2D = null
 var _flash_ring: NeonPiece = null
 var _wash: NeonPiece = null
 
@@ -103,6 +118,8 @@ func _ready() -> void:
 		_build_crafter_pieces()
 	elif building_type == GameState.BUILDING_MOTHERSHIP:
 		_build_mothership_pieces()
+	elif building_type == GameState.BUILDING_TRANSPORT_HUB:
+		_build_hub_pieces()
 	queue_redraw()
 
 
@@ -121,6 +138,8 @@ func apply_animation() -> void:
 			_animate_mothership()
 		GameState.BUILDING_SHIP_CRAFTER:
 			_animate_crafter()
+		GameState.BUILDING_TRANSPORT_HUB:
+			_animate_transport_hub()
 
 
 # Where the satellites are, and how open the reactor core is. Both are read
@@ -161,6 +180,8 @@ func _draw() -> void:
 			_draw_command_center()
 		GameState.BUILDING_MOTHERSHIP:
 			_draw_mothership_static(self)
+		GameState.BUILDING_TRANSPORT_HUB:
+			_draw_transport_hub_static(self)
 		_:
 			_draw_crafter_static(self)
 
@@ -203,6 +224,50 @@ const CMD_TOKEN_RADIUS: float = 9.0
 const CMD_STUD_RADIUS: float = 7.0
 
 
+# --- transport hub --------------------------------------------------------
+
+func _draw_transport_hub_static(target: CanvasItem) -> void:
+	var c: Color = TRANSPORT_HUB_COLOR
+
+	# Dock ring and the deck nested inside it.
+	NeonDraw.draw_glowing_polygon(target, _ring(Vector2.ZERO, HUB_RING_RADIUS, HUB_BERTH_COUNT, PI / 8.0), c, 1.0)
+	NeonDraw.draw_glowing_polygon(target, _ring(Vector2.ZERO, HUB_DECK_RADIUS, HUB_BERTH_COUNT, PI / 8.0), c, 0.45, NeonDraw.DEFAULT_CORE, 0.7)
+
+	# Freight core: a squared-off hold rather than a reactor, so it reads as
+	# storage and not as another power plant.
+	NeonDraw.draw_glowing_polygon(target, _ring(Vector2.ZERO, HUB_CORE_RADIUS, 4, PI / 4.0), c, 0.95)
+
+	for i in range(HUB_BERTH_COUNT):
+		var a: float = (float(i) / HUB_BERTH_COUNT) * TAU + PI / 8.0
+		var dir: Vector2 = Vector2(cos(a), sin(a))
+		NeonDraw.draw_glowing_line(target, dir * HUB_CORE_RADIUS, dir * HUB_DECK_RADIUS, c, 0.5, 0.32)
+		# Berth arm standing off the ring, where a transporter parks.
+		NeonDraw.draw_glowing_line(target, dir * HUB_RING_RADIUS,
+			dir * (HUB_RING_RADIUS + HUB_BERTH_LENGTH), c, 0.75, 0.38)
+
+
+func _build_hub_pieces() -> void:
+	# Stationed transports, as NeonPiece children of one holder that turns.
+	# Per #10 the geometry is rasterised once and only the holder's rotation
+	# changes, so the traffic costs no redraws at all.
+	_hub_traffic = Node2D.new()
+	add_child(_hub_traffic)
+	for i in range(HUB_DOCKED_COUNT):
+		var a: float = (float(i) / HUB_DOCKED_COUNT) * TAU
+		var at: Vector2 = Vector2(cos(a), sin(a)) * HUB_DOCKED_ORBIT
+		var piece: NeonPiece = NeonPiece.create(_hub_traffic, at, TRANSPORT_HUB_COLOR)
+		# A stubby freighter: blunt, boxy, nothing like the fleet's darts.
+		piece.add_polygon(PackedVector2Array([
+			Vector2(-9, -5), Vector2(9, -5), Vector2(12, 0), Vector2(9, 5), Vector2(-9, 5),
+		]))
+		piece.rotation = a + PI / 2.0
+		piece.queue_redraw()
+
+
+func _animate_transport_hub() -> void:
+	_hub_traffic.rotation = phase_time * HUB_SPIN_SPEED
+
+
 func _diamond(centre: Vector2, r: float) -> PackedVector2Array:
 	return PackedVector2Array([
 		centre + Vector2(0, -r), centre + Vector2(r, 0),