feat(audio): add AudioManager with floor music cross-fade and SFX

Replaces placeholder AudioManager with full implementation: floor-based
music routing via _derive_floor_from_room, cross-fade tween between
AudioStreamPlayers, SFX event-key dispatch, and room-change guard to
prevent redundant load attempts. 11 new tests (207 total, 206 passing).

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

scripts/autoload/AudioManager.gd

@@ -1,63 +1,128 @@
-## AudioManager — music playback with cross-fade, SFX playback, volume control.
+## AudioManager — floor music with cross-fade and SFX for player interactions.
+## Autoload registered in project.godot. No class_name (Godot 4 autoload conflict).
 extends Node
 
-const DEFAULT_MUSIC_VOLUME: float = 0.6
+const CROSSFADE_DURATION: float = 0.8
-const CROSSFADE_DURATION: float = 1.0
 
-var _music_player_a: AudioStreamPlayer
+const _MUSIC_MAP: Dictionary = {
-var _music_player_b: AudioStreamPlayer
+	0: "res://assets/audio/music/floor_0.ogg",
+	1: "res://assets/audio/music/floor_1.ogg",
+	2: "res://assets/audio/music/floor_2.ogg",
+	3: "res://assets/audio/music/floor_3.ogg",
+}
+
+const _SFX_MAP: Dictionary = {
+	"chest_tap":         "res://assets/audio/sfx/chest_tap.ogg",
+	"item_spawn":        "res://assets/audio/sfx/item_spawn.ogg",
+	"item_drag_start":   "res://assets/audio/sfx/item_drag_start.ogg",
+	"item_drop_hand":    "res://assets/audio/sfx/item_drop_hand.ogg",
+	"item_drop_outfit":  "res://assets/audio/sfx/item_drop_outfit.ogg",
+	"item_return_chest": "res://assets/audio/sfx/item_return_chest.ogg",
+	"item_drop_floor":   "res://assets/audio/sfx/item_drop_floor.ogg",
+}
+
+var _current_floor: int = -1
+var _is_crossfading: bool = false
 var _active_player: AudioStreamPlayer
+var _last_room: String = ""
+
+var _music_a: AudioStreamPlayer
+var _music_b: AudioStreamPlayer
 var _sfx_player: AudioStreamPlayer
-var _music_volume: float = DEFAULT_MUSIC_VOLUME
-var _sfx_volume: float = 1.0
-var _is_fading: bool = false
 
 
 func _ready() -> void:
-	_music_player_a = AudioStreamPlayer.new()
+	_music_a = AudioStreamPlayer.new()
-	_music_player_b = AudioStreamPlayer.new()
+	_music_b = AudioStreamPlayer.new()
 	_sfx_player = AudioStreamPlayer.new()
-	add_child(_music_player_a)
+	add_child(_music_a)
-	add_child(_music_player_b)
+	add_child(_music_b)
 	add_child(_sfx_player)
-	_active_player = _music_player_a
+	_active_player = _music_a
-	_apply_music_volume()
+	_music_a.volume_db = linear_to_db(GameState.music_volume)
+	_music_b.volume_db = linear_to_db(0.0)
+	_sfx_player.volume_db = linear_to_db(GameState.sfx_volume)
+	GameState.state_changed.connect(_on_game_state_changed)
+	_last_room = GameState.current_room
+	var initial_floor: int = _derive_floor_from_room(GameState.current_room)
+	if initial_floor != -1:
+		play_floor_music(initial_floor)
 
 
-func play_music(stream: AudioStream) -> void:
+func play_floor_music(floor: int) -> void:
-	if _active_player.stream == stream and _active_player.playing:
+	if floor == _current_floor:
 		return
-	var next_player: AudioStreamPlayer = _music_player_b if _active_player == _music_player_a else _music_player_a
+	if not _MUSIC_MAP.has(floor):
-	next_player.stream = stream
+		return
-	next_player.volume_db = linear_to_db(0.0)
+	if _is_crossfading:
-	next_player.play()
+		return
-	var prev_player: AudioStreamPlayer = _active_player
+	_is_crossfading = true
-	_active_player = next_player
+	_current_floor = floor
-	var tween: Tween = create_tween()
+	var inactive: AudioStreamPlayer = _music_b if _active_player == _music_a else _music_a
-	tween.set_parallel(true)
+	var path: String = _MUSIC_MAP[floor]
-	tween.tween_property(prev_player, "volume_db", linear_to_db(0.0), CROSSFADE_DURATION)
+	if not ResourceLoader.exists(path):
-	tween.tween_property(next_player, "volume_db", linear_to_db(_music_volume), CROSSFADE_DURATION)
+		_is_crossfading = false
-	tween.chain().tween_callback(prev_player.stop)
+		return
+	var stream: AudioStream = load(path) as AudioStream
+	if stream == null:
+		_is_crossfading = false
+		return
+	inactive.stream = stream
+	inactive.volume_db = linear_to_db(0.0)
+	inactive.play()
+	var tween: Tween = create_tween().set_parallel(true)
+	tween.tween_property(inactive, "volume_db", linear_to_db(GameState.music_volume), CROSSFADE_DURATION)
+	tween.tween_property(_active_player, "volume_db", linear_to_db(0.0), CROSSFADE_DURATION)
+	await tween.finished
+	_active_player.stop()
+	_active_player = inactive
+	_is_crossfading = false
 
 
-func play_sfx(stream: AudioStream) -> void:
+func play_sfx(event: String) -> void:
+	if not _SFX_MAP.has(event):
+		return
+	var path: String = _SFX_MAP[event]
+	if not ResourceLoader.exists(path):
+		return
+	var stream: AudioStream = load(path) as AudioStream
+	if stream == null:
+		return
 	_sfx_player.stream = stream
-	_sfx_player.volume_db = linear_to_db(_sfx_volume)
 	_sfx_player.play()
 
 
-func set_music_volume(value: float) -> void:
+func set_music_volume(vol: float) -> void:
-	_music_volume = clampf(value, 0.0, 1.0)
+	GameState.music_volume = vol
-	_apply_music_volume()
+	_active_player.volume_db = linear_to_db(vol)
 
 
-func set_sfx_volume(value: float) -> void:
+func set_sfx_volume(vol: float) -> void:
-	_sfx_volume = clampf(value, 0.0, 1.0)
+	GameState.sfx_volume = vol
+	_sfx_player.volume_db = linear_to_db(vol)
 
 
-func get_music_volume() -> float:
+func get_current_floor() -> int:
-	return _music_volume
+	return _current_floor
 
 
-func _apply_music_volume() -> void:
+func _on_game_state_changed() -> void:
-	_active_player.volume_db = linear_to_db(_music_volume)
+	if GameState.current_room == _last_room:
+		return
+	_last_room = GameState.current_room
+	var floor: int = _derive_floor_from_room(GameState.current_room)
+	if floor != -1:
+		play_floor_music(floor)
+
+
+func _derive_floor_from_room(room: String) -> int:
+	match room:
+		"reception", "giftshop", "restaurant", "emergency":
+			return 0
+		"xray", "pharmacy", "lab", "patient_rooms":
+			return 1
+		"ultrasound", "delivery_room", "nursery":
+			return 2
+		"garden_party":
+			return 3
+	return -1

test/unit/test_audio_manager.gd

@@ -0,0 +1,71 @@
+## Tests for AudioManager — floor derivation, no-op guard, SFX key validation.
+extends GutTest
+
+
+func before_each() -> void:
+	AudioManager._current_floor = -1
+	AudioManager._is_crossfading = false
+
+
+func test_derive_floor_floor0_reception() -> void:
+	assert_eq(AudioManager._derive_floor_from_room("reception"), 0)
+
+
+func test_derive_floor_floor0_all_rooms() -> void:
+	assert_eq(AudioManager._derive_floor_from_room("giftshop"), 0)
+	assert_eq(AudioManager._derive_floor_from_room("restaurant"), 0)
+	assert_eq(AudioManager._derive_floor_from_room("emergency"), 0)
+
+
+func test_derive_floor_floor1_all_rooms() -> void:
+	assert_eq(AudioManager._derive_floor_from_room("xray"), 1)
+	assert_eq(AudioManager._derive_floor_from_room("pharmacy"), 1)
+	assert_eq(AudioManager._derive_floor_from_room("lab"), 1)
+	assert_eq(AudioManager._derive_floor_from_room("patient_rooms"), 1)
+
+
+func test_derive_floor_floor2_all_rooms() -> void:
+	assert_eq(AudioManager._derive_floor_from_room("ultrasound"), 2)
+	assert_eq(AudioManager._derive_floor_from_room("delivery_room"), 2)
+	assert_eq(AudioManager._derive_floor_from_room("nursery"), 2)
+
+
+func test_derive_floor_garden() -> void:
+	assert_eq(AudioManager._derive_floor_from_room("garden_party"), 3)
+
+
+func test_derive_floor_unknown_returns_minus_one() -> void:
+	assert_eq(AudioManager._derive_floor_from_room("unknown_room"), -1)
+	assert_eq(AudioManager._derive_floor_from_room(""), -1)
+
+
+func test_get_current_floor_starts_at_minus_one() -> void:
+	assert_eq(AudioManager.get_current_floor(), -1)
+
+
+func test_play_floor_music_same_floor_is_noop() -> void:
+	AudioManager._current_floor = 0
+	AudioManager.play_floor_music(0)
+	assert_eq(AudioManager.get_current_floor(), 0)
+
+
+func test_play_sfx_unknown_key_does_not_crash() -> void:
+	AudioManager.play_sfx("nonexistent_event_xyz")
+	pass
+
+
+func test_sfx_map_has_all_seven_keys() -> void:
+	assert_true(AudioManager._SFX_MAP.has("chest_tap"))
+	assert_true(AudioManager._SFX_MAP.has("item_spawn"))
+	assert_true(AudioManager._SFX_MAP.has("item_drag_start"))
+	assert_true(AudioManager._SFX_MAP.has("item_drop_hand"))
+	assert_true(AudioManager._SFX_MAP.has("item_drop_outfit"))
+	assert_true(AudioManager._SFX_MAP.has("item_return_chest"))
+	assert_true(AudioManager._SFX_MAP.has("item_drop_floor"))
+
+
+func test_music_map_has_all_four_floors() -> void:
+	assert_true(AudioManager._MUSIC_MAP.has(0))
+	assert_true(AudioManager._MUSIC_MAP.has(1))
+	assert_true(AudioManager._MUSIC_MAP.has(2))
+	assert_true(AudioManager._MUSIC_MAP.has(3))