feat(client): add tile rendering, fog overlay, and camera smoothing

Sprint 2 rendering pipeline: tiles (#129), fog (#131), camera (#116).

- tile_renderer.gd: programmatic TileSet with floor/wall/door/object
  placeholder tiles, renders from snapshot tile data
- fog_renderer.gd: TileMapLayer overlay with three visibility states
  (visible/fog-edge/hidden), computed from visible_positions data
- Camera2D: smoothing enabled (speed 6.0), 2x zoom, locked to player
- game_state.gd: stores visible_tiles and visible_positions from snapshots
- sim_bridge.gd: test data with 8x8 room, corridor, and Manhattan
  distance visibility for development without server
- Scene render order: Tiles -> FogOverlay -> Entities
- Background clear color set to near-black for unexplored areas

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/scripts/autoloads/sim_bridge.gd

@@ -235,7 +235,7 @@ static func _action_enum_to_wire(action: int) -> String:
 			return ""
 
 # Hardcoded test snapshot matching Protocol format (deterministic per D-010 principle 4).
-# Uses the same {tick, entities} schema as Protocol.decode_snapshot() returns.
+# Uses the same {tick, entities, tiles} schema as Protocol.decode_snapshot() returns.
 func _test_snapshot() -> Dictionary:
 	_test_tick += 1
 	return {
@@ -246,7 +246,71 @@ func _test_snapshot() -> Dictionary:
 				"x": 10.0,
 				"y": 10.0,
 				"z": 0,
+				"kind": { "variant": "Player", "data": null },
+			},
+			{
+				"entity_id": 2,
+				"x": 12.0,
+				"y": 10.0,
+				"z": 0,
 				"kind": { "variant": "Npc", "data": null },
 			},
 		],
+		"tiles": _test_tiles(),
+		"visible_positions": _test_visible_positions(),
 	}
+
+# Generate a small test room: 8x6 room with walls, a door, and floor
+func _test_tiles() -> Array:
+	var tiles: Array = []
+	var room_x := 7
+	var room_y := 7
+	var room_w := 8
+	var room_h := 8
+
+	for x in range(room_x, room_x + room_w):
+		for y in range(room_y, room_y + room_h):
+			var is_edge := (x == room_x or x == room_x + room_w - 1
+				or y == room_y or y == room_y + room_h - 1)
+			var tile_type: String
+			if is_edge:
+				# Door on the south wall, center
+				if y == room_y + room_h - 1 and x == room_x + room_w / 2:
+					tile_type = "door"
+				else:
+					tile_type = "wall"
+			else:
+				tile_type = "floor"
+			tiles.append({"x": x, "y": y, "z": 0, "type": tile_type})
+
+	# Corridor south of the door
+	var door_x := room_x + room_w / 2
+	for y in range(room_y + room_h, room_y + room_h + 4):
+		tiles.append({"x": door_x - 1, "y": y, "z": 0, "type": "wall"})
+		tiles.append({"x": door_x, "y": y, "z": 0, "type": "floor"})
+		tiles.append({"x": door_x + 1, "y": y, "z": 0, "type": "wall"})
+
+	return tiles
+
+# Test visibility: player at (10,10) can see tiles within radius 4, blocked by walls
+func _test_visible_positions() -> Array:
+	var positions: Array = []
+	var player_x := 10
+	var player_y := 10
+	var radius := 4
+
+	# Room bounds (inner floor area)
+	var room_x := 7
+	var room_y := 7
+	var room_w := 8
+	var room_h := 8
+
+	for x in range(player_x - radius, player_x + radius + 1):
+		for y in range(player_y - radius, player_y + radius + 1):
+			var dist := absf(x - player_x) + absf(y - player_y)
+			if dist <= radius:
+				# Walls are visible but block further vision
+				# For test purposes, include all tiles within radius that are inside the room
+				if x >= room_x and x < room_x + room_w and y >= room_y and y < room_y + room_h:
+					positions.append({"x": x, "y": y})
+	return positions