#138: structures and doctrines cost more than rocks, and more the deeper they are

Both halves of the ticket, in the shape vessels have used since gas bombers
and laser ships: a definition carries an ore figure and, when it wants more
than ore, a dictionary that IS the price. `building_costs()` and
`skill_costs()` answer it the way `product_costs()` already did, so there is
one question with one answer whatever is being bought, and every payment
path now goes through `spend_resources` rather than `spend`.

Seven of ten structures and thirteen of seventeen doctrines now want gas,
energy or dark matter alongside their rocks, and the totals climb with tree
depth - structures 16/31/58/62/96 by depth, doctrines 15/30/73/96/143/258/530.

The constraint that shaped the table is REACHABILITY, and it is the reason
some prices stayed ore-only. Energy exists only where a gas burner stands,
and a gas burner needs Power Systems - so nothing at or before that depth
may be priced in energy, or it is a wall with no way through. Dark matter is
rarer still and appears once, on the deepest node in the game. The extractor
stays rocks-only despite its depth allowing gas, because the quest chain
reaches it before it has sent the player for any.

test_progressive_costs checks those as properties rather than transcribing
the numbers, so rebalancing a price costs nothing while breaking the shape
fails: nothing unreachable at its own depth, prices rising with depth, the
ore field agreeing with the dictionary (repairs quote the field alone, since
a repair drone carries ore and nothing else), and the quest chain never
asking for a structure it has not funded.

Two things cleaned up on the way:

- The per-building cost constants in GameState are gone. Nothing but tests
  used them, and they were a second copy of a number the definitions already
  hold - exactly what would drift once a price gained a resource.
- research_for_building() returns a display NAME, and the id-keyed half of
  the tree wants an id. That mix-up is silent - skill_depth() of a name finds
  no node and answers 0, so a deep structure reads as an ungated one, which
  is how the first draft of the test let an unreachable price through.
  research_node_for_building() is the id, and the name is expressed from it.

PriceTag no longer rebuilds its labels when re-told the same price; it
refreshes the held figures instead. The craft menu re-states prices every
frame and the build menu now does too, so that was a dozen Labels being torn
down and rebuilt sixty times a second.

buildings/BuildingDefinition.gd

@@ -4,7 +4,17 @@ extends Resource
 @export var definition_id: String
 @export var display_name: String
 @export_multiline var description: String
+# What it costs in ORE, and the whole price when it wants more than ore.
+#
+# #138: structures all charged rocks and nothing else, whatever they were.
+# The dictionary is the same shape VesselDefinition has used since gas
+# bombers and laser ships (build_cost / build_resource_costs): when it is
+# empty the price is `cost` in ore, and when it is set it IS the price, ore
+# included - and its ore entry must agree with `cost`, which the test pins,
+# because repair costs are quoted from `cost` alone (a repair drone carries
+# ore and nothing else).
 @export var cost: int
+@export var build_resource_costs: Dictionary = {}
 @export var action_icon: int
 @export var menu_icon: int
 @export var visual_scene: PackedScene

buildings/CommandBuildingDefinition.tres

@@ -7,6 +7,7 @@ definition_id = "command_center"
 display_name = "Command Center"
 description = "Fly the fleet onto it to drag your fleet into a new formation. Rebuilt fleets keep it."
 cost = 15
+build_resource_costs = {"ore": 15, "gas": 6}
 action_icon = 10
 menu_icon = 10
 visual_scene = ExtResource("2")

buildings/GasBurnerBuildingDefinition.tres

@@ -20,7 +20,8 @@ script = ExtResource("1")
 definition_id = "gas_burner"
 display_name = "Gas Burner"
 description = "Burns gas into energy at its own site. Hub transporters keep it stocked with gas and collect the energy it makes."
-cost = 30
+cost = 40
+build_resource_costs = {"ore": 40, "gas": 22}
 action_icon = 33
 menu_icon = 33
 visual_scene = ExtResource("2")

buildings/OutpostBuildingDefinition.tres

@@ -7,6 +7,7 @@ definition_id = "outpost"
 display_name = "Outpost"
 description = "A forward position for the fleet to garrison. Vessels stationed here hold station and fight what comes at them, without you flying back."
 cost = 30
+build_resource_costs = {"ore": 30, "gas": 16}
 action_icon = 40
 menu_icon = 40
 visual_scene = ExtResource("2")

buildings/PlanningBuildingDefinition.tres

@@ -6,7 +6,8 @@ script = ExtResource("1")
 definition_id = "planning_center"
 display_name = "Planning Center"
 description = "Holds standing orders for the whole game: say how many of each vessel should always exist, and the ship crafters are kept working until they do."
-cost = 70
+cost = 50
+build_resource_costs = {"ore": 50, "gas": 30}
 action_icon = 41
 menu_icon = 41
 visual_scene = ExtResource("2")

buildings/ShipLabBuildingDefinition.tres

@@ -6,7 +6,8 @@ script = ExtResource("1")
 definition_id = "ship_lab"
 display_name = "Ship Lab"
 description = "Fly the fleet onto it to upgrade each vessel type and unlock new vessel designs."
-cost = 35
+cost = 30
+build_resource_costs = {"ore": 30, "gas": 18}
 action_icon = 13
 menu_icon = 13
 visual_scene = ExtResource("2")

buildings/TransportHubBuildingDefinition.tres

@@ -6,7 +6,8 @@ script = ExtResource("1")
 definition_id = "transport_hub"
 display_name = "Transport Hub"
 description = "Stations transport vessels. They collect extracted resources and supply buildings that are waiting on materials."
-cost = 30
+cost = 28
+build_resource_costs = {"ore": 28, "gas": 20}
 action_icon = 12
 menu_icon = 12
 visual_scene = ExtResource("2")

buildings/WorkshopBuildingDefinition.tres

@@ -6,7 +6,8 @@ script = ExtResource("1")
 definition_id = "spacial_workshop"
 display_name = "Spacial Workshop"
 description = "Sends repair drones out to damaged structures. Repairs cost ore in proportion to the damage, delivered here by hub transporters."
-cost = 55
+cost = 50
+build_resource_costs = {"ore": 50, "gas": 28, "energy": 18}
 action_icon = 42
 menu_icon = 42
 visual_scene = ExtResource("2")