Phase 5 cabin polish — door, floor, interior crate, double-render fix

Make the demo cabin readable as a real building so the rendering pattern
is solid before Phase 6+ adds more building types.

Demo seed (world.gd._seed_phase5_demo_buildings):
- 8×6 stone cabin at (44, 23) — 23 walls (perimeter minus door slot) +
  1 door (south wall centre at (47, 28)) + 24 wood-floor designations
  for the interior. ConstructionProvider picks them all up; pawns build
  the whole thing.
- One pre-built crate inside at (50, 24) so the interior reads as a
  furnished room on first frame.
- Two external stockpile-target crates unchanged at (17, 60) / (18, 60).

Door visual rewrite (door.gd):
- Was the old 16×24 bottom-anchored shape that encroached on the cell
  above. Now fits strictly within its 16×16 tile, matching the wall's
  3/4 band layout (5 px lit lintel + 11 px shaded frame + inset panel
  + hinge dot). Door and walls now share a top horizon line so they
  line up visually.

Designation gained TOOL_BUILD_DOOR + atlas mapping; world.gd's
_on_designation_added now branches on build_door to spawn a Door entity.

THE DOUBLE-RENDER BUG (caught by MCP inspection):
- World.mark_floor_tile stamps the Floor TileMap with atlas (2, 0) which
  is *stone-grey* in the placeholder atlas, regardless of material name.
- The Floor TileMap layer was visible=true with z_index=1, so it drew
  ON TOP of the brown Floor entity sprites underneath.
- Result before fix: interior tiles looked gray-stone, not wood.
- Fix: set Floor TileMap layer visible=false (data-only, same as Wall).
  Entities own the visual; the TileMap retains tile-level data for
  Phase 13's room detection + Phase 16's save format.

Pattern locked for future building types: 'render at entity level,
TileMap layers are data-only'. Phase 13's roof and any future wall
materials follow the same template.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scenes/world/designation.gd

@@ -16,12 +16,15 @@ class_name Designation
 const TOOL_NONE:        StringName = &"none"
 const TOOL_BUILD_WALL:  StringName = &"build_wall"
 const TOOL_BUILD_FLOOR: StringName = &"build_floor"
+const TOOL_BUILD_DOOR:  StringName = &"build_door"
 
 # Atlas coords on the shared placeholder tileset (source 0).
 # build_wall → stone-grey (2, 0); build_floor → dirt-brown (1, 0).
+# build_door → dark stone (3, 0) so the ghost reads visually distinct from walls.
 const _ATLAS_BY_TOOL: Dictionary = {
 	&"build_wall":  Vector2i(2, 0),
 	&"build_floor": Vector2i(1, 0),
+	&"build_door":  Vector2i(3, 0),
 }
 
 # Placeholder source ID — mirrors World.PLACEHOLDER_SOURCE_ID.
@@ -60,7 +63,7 @@ func bind(paint_layer: TileMapLayer, selection: Selection = null) -> void:
 ## Activate a paint tool.  Pass TOOL_NONE to deactivate.
 func set_active_tool(tool: StringName) -> void:
 	assert(
-		tool in [TOOL_NONE, TOOL_BUILD_WALL, TOOL_BUILD_FLOOR],
+		tool in [TOOL_NONE, TOOL_BUILD_WALL, TOOL_BUILD_FLOOR, TOOL_BUILD_DOOR],
 		"Designation.set_active_tool: unknown tool '%s'" % tool
 	)
 	_tool = tool

scenes/world/world.gd

@@ -215,33 +215,64 @@ func _spawn_sample_harvestables() -> void:
 
 
 func _seed_phase5_demo_buildings() -> void:
-	# Pre-queue a small cabin outline as build designations so pawns visibly
-	# construct walls when they exit Chop/Mine work. Phase 17 will add real
-	# player-driven designation UI; for now the player sees the construction
-	# loop without needing to paint anything.
+	# Pre-queue a furnished cabin so the construction loop runs end-to-end
+	# without needing player-paint UI (deferred to Phase 17).
 	#
-	# Layout: 8×6 wall ring at (44, 23) — interior 6×4 = 24 cells of real room.
+	# Layout — 8×6 stone cabin at (44, 23), south door, wood floor inside:
+	#   • Perimeter walls (skipping the door slot)
+	#   • Door at (47, 28) — middle of the south wall
+	#   • Wood floor across the 6×4 interior
+	#   • One pre-built crate inside (north-east corner of the interior)
+	#   • Two stockpile-target crates outside (Phase 4 hauling target)
 	var origin := Vector2i(44, 23)
 	var w := 8
 	var h := 6
+	var door_x := w / 2 - 1  # 3 → tile (47, y_bottom). Centred door.
+	var door_tile := origin + Vector2i(door_x, h - 1)
+
+	# Perimeter walls — skip the door slot in the bottom row.
+	var wall_count := 0
 	for x in w:
 		EventBus.designation_added.emit(origin + Vector2i(x, 0), Designation.TOOL_BUILD_WALL)
-		EventBus.designation_added.emit(origin + Vector2i(x, h - 1), Designation.TOOL_BUILD_WALL)
-	for y in h:
+		wall_count += 1
+		var bottom_tile := origin + Vector2i(x, h - 1)
+		if bottom_tile != door_tile:
+			EventBus.designation_added.emit(bottom_tile, Designation.TOOL_BUILD_WALL)
+			wall_count += 1
+	for y in range(1, h - 1):  # left + right cols, skip corners (already painted as top/bottom rows)
 		EventBus.designation_added.emit(origin + Vector2i(0, y), Designation.TOOL_BUILD_WALL)
 		EventBus.designation_added.emit(origin + Vector2i(w - 1, y), Designation.TOOL_BUILD_WALL)
-	# Place a couple of crates at known tiles so the haul system has a target.
+		wall_count += 2
+
+	# Door at south wall centre.
+	EventBus.designation_added.emit(door_tile, Designation.TOOL_BUILD_DOOR)
+
+	# Wood floor across the interior — 6×4 = 24 cells.
+	var floor_count := 0
+	for x in range(1, w - 1):
+		for y in range(1, h - 1):
+			EventBus.designation_added.emit(origin + Vector2i(x, y), Designation.TOOL_BUILD_FLOOR)
+			floor_count += 1
+
+	# Pre-built crate inside the cabin (top-right corner of interior).
+	# Auto-built so the cabin shows furnished on first frame.
+	var interior_crate: Crate = CRATE_SCENE.instantiate()
+	add_child(interior_crate)
+	interior_crate.setup(origin + Vector2i(w - 2, 1))  # (50, 24)
+	while interior_crate.is_buildable():
+		interior_crate.on_build_tick()
+
+	# Two external stockpile-target crates south-west (Phase 4 haul destination).
 	var crate_tiles: Array[Vector2i] = [Vector2i(17, 60), Vector2i(18, 60)]
 	for t in crate_tiles:
 		var c: Crate = CRATE_SCENE.instantiate()
 		add_child(c)
 		c.setup(t)
-		# Mark crate as already-built for the demo (skip the construction phase).
-		# Phase 17 player UI flow would walk it through a build designation first.
 		while c.is_buildable():
 			c.on_build_tick()
-	Audit.log("world", "phase 5 demo: %d wall designations seeded + %d crates built" % [
-		w * 2 + h * 2 - 4, crate_tiles.size()
+
+	Audit.log("world", "phase 5 demo: %d walls + 1 door + %d floors queued; %d crates pre-built" % [
+		wall_count, floor_count, 1 + crate_tiles.size()
 	])
 
 
@@ -289,6 +320,10 @@ func _on_designation_added(cell: Vector2i, tool: StringName) -> void:
 			entity = FLOOR_SCENE.instantiate()
 			add_child(entity)
 			entity.setup(cell, &"wood")
+		&"build_door":
+			entity = DOOR_SCENE.instantiate()
+			add_child(entity)
+			entity.setup(cell)
 		_:
 			Audit.log("world", "unknown designation tool: %s" % tool)
 			return

scenes/world/world.tscn

@@ -20,6 +20,7 @@ z_index = 0
 
 [node name="Floor" type="TileMapLayer" parent="."]
 z_index = 1
+visible = false
 
 [node name="Wall" type="TileMapLayer" parent="."]
 z_index = 2