feat(@projects/@magic-civilization): ✨ add river gap blocking for bunkers

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

src/game/engine/scenes/tests/bunker_proof.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3 uid="uid://bnkr76proof1"]
+
+[ext_resource type="Script" path="res://engine/scenes/tests/bunker_proof.gd" id="1_script"]
+
+[node name="BunkerProof" type="Node2D"]
+script = ExtResource("1_script")

src/game/engine/src/modules/management/improvement_manager.gd

@@ -34,10 +34,15 @@ func get_buildable_improvements(
 			continue
 
 		var data: Dictionary = ImprovementScript._get_data(imp_id)
-		var tech_req: String = str(data.get("tech_required", ""))
+		# `requires_tech` is the canonical field per improvements.schema.json
+		# (units/buildings use `tech_required`; improvements do not).
+		var tech_req: String = str(data.get("requires_tech", ""))
 		if tech_req != "" and tech_req != "null" and not player.has_tech(tech_req):
 			continue
 
+		if _river_gap_blocked(data, unit.position):
+			continue
+
 		result.append({
 			"id": imp_id,
 			"name": data.get("name", imp_id),
@@ -47,6 +52,20 @@ func get_buildable_improvements(
 	return result
 
 
+func _river_gap_blocked(data: Dictionary, tile_pos: Vector2i) -> bool:
+	## Deposit-destroying improvements (bunker) cannot be sited on a
+	## river-course tile until p2-78 lands the windowed hydrology re-solve.
+	## The verdict comes from Rust (`GdGameState.bunker_river_gap_blocked`);
+	## this is only the build-validity consultation.
+	var effects: Dictionary = data.get("effects", {}) as Dictionary
+	if not bool(effects.get("destroys_deposit", false)):
+		return false
+	var gd_state: RefCounted = GameState.get_gd_state()
+	if gd_state == null:
+		return false
+	return bool(gd_state.call("bunker_river_gap_blocked", tile_pos.x, tile_pos.y))
+
+
 func _can_unit_build_at(
 	unit: RefCounted, game_map: RefCounted, player: RefCounted
 ) -> bool:

src/game/engine/tests/unit/test_worker_improvement_tech_gate.gd

@@ -1,5 +1,5 @@
 extends GutTest
-## p0-16 acceptance test: when an improvement declares `tech_required`, the
+## p0-16 acceptance test: when an improvement declares `requires_tech`, the
 ## worker's candidate list MUST exclude it for a player that lacks the tech.
 ##
 ## ImprovementManager.get_buildable_improvements applies the tech gate via
@@ -40,7 +40,7 @@ func before_all() -> void:
 		"valid_terrain": ["grassland", "plains"],
 		"yields": {"food": 1, "production": 1},
 		"effects": {},
-		"tech_required": FIXTURE_TECH_ID,
+		"requires_tech": FIXTURE_TECH_ID,
 	}
 
 
@@ -116,3 +116,58 @@ func test_worker_with_required_tech_includes_gated_improvement() -> void:
 		("worker WITH '%s' tech must be offered '%s'; candidate list "
 			+ "was %s") % [FIXTURE_TECH_ID, FIXTURE_IMP_ID, str(ids)],
 	)
+
+
+func test_bunker_gated_by_terrain_and_pneumatic_construction() -> void:
+	## p2-76 acceptance: the SHIPPING bunker is offered only on hills/mountains
+	## AND only with `pneumatic_construction` (both gates read from bunker.json).
+	var bunker_data: Dictionary = DataLoader.get_improvement("bunker")
+	assert_false(bunker_data.is_empty(), "bunker.json must be loaded by the pack")
+
+	var mgr: RefCounted = ImprovementManagerScript.new()
+	var game_map: RefCounted = GameMapScript.new()
+	game_map.initialize(4, 4, 0)
+	var tile: Resource = TileScript.new()
+	tile.biome_id = "hills"
+	tile.owner = 0
+	tile.improvement = ""
+	tile.position = Vector2i(0, 0)
+	game_map.set_tile(Vector2i(0, 0), tile)
+
+	var player: RefCounted = PlayerScript.new()
+	player.index = 0
+	player.researched_techs.clear()
+
+	var worker: RefCounted = UnitScript.new("worker", 0, Vector2i(0, 0))
+	worker.can_build_improvements = true
+	worker.movement_remaining = 1
+
+	var without_tech: Array = mgr.get_buildable_improvements(worker, game_map, player)
+	var ids_without: Array[String] = []
+	for entry: Dictionary in without_tech:
+		ids_without.append(str(entry.get("id", "")))
+	assert_false(
+		"bunker" in ids_without,
+		"bunker must NOT be offered without pneumatic_construction; got %s" % str(ids_without),
+	)
+
+	player.researched_techs.append("pneumatic_construction")
+	var with_tech: Array = mgr.get_buildable_improvements(worker, game_map, player)
+	var ids_with: Array[String] = []
+	for entry: Dictionary in with_tech:
+		ids_with.append(str(entry.get("id", "")))
+	assert_true(
+		"bunker" in ids_with,
+		"bunker MUST be offered on hills with pneumatic_construction; got %s" % str(ids_with),
+	)
+
+	# Terrain gate: same teched player on grassland must not see the bunker.
+	tile.biome_id = "grassland"
+	var on_grass: Array = mgr.get_buildable_improvements(worker, game_map, player)
+	var ids_grass: Array[String] = []
+	for entry: Dictionary in on_grass:
+		ids_grass.append(str(entry.get("id", "")))
+	assert_false(
+		"bunker" in ids_grass,
+		"bunker must NOT be offered on grassland; got %s" % str(ids_grass),
+	)