feat(audio): Sprint 13 — AudioManager, zone crossfade, dip profiles, murmur wiring (#528, #529, #530, #533)

AudioManager: volume slider persistence (ConfigFile), settings UI with
5 teal-bordered sliders, default_bus_layout.tres for editor. Zone
crossfade: defensive zone_id read from snapshot tiles, 1.5-2s ambient
tween, auto-activates when server ships OQ-09. Dip profiles: dialogue
dip in show/hide_dialogue, ListeningFocus 30-tick gate via
stationary_ticks in game_state.gd. NPC murmur: client plumbing for
event-driven World SFX playback, no-ops until audio asset arrives.

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

client/scripts/main.gd

@@ -15,6 +15,7 @@ extends Node2D
 @onready var gauntlet_hud = $UILayer/GauntletHUD  # #496: room timer + personal bests
 @onready var checklist_overlay = $UILayer/ChecklistOverlay  # #503: auto-checklist progress
 @onready var bug_report_dialog = $ModalLayer/BugReportDialog  # #495: F12 WRONG button
+@onready var settings_dialog = $ModalLayer/SettingsDialog     # #528: audio settings (ESC/OPEN_MENU)
 
 var _last_dialogue_npc_id: int = -1  # D-064: NPC entity_id for WalkAway input
 var _camera_anchored: bool = false
@@ -24,6 +25,9 @@ var _known_recognition_ids: Dictionary = {}  # D-067: entity_ids that have alrea
 var _flash_rect: ColorRect = null  # #502/#501: ephemeral screen flash overlay (shared: teleport preempts amber)
 var _teleport_in_progress: bool = false  # #501: defer smoothing re-enable by one frame after teleport
 var _pending_record_inputs: Array = []   # #507: accumulates server-bound inputs across frames; flushed into record_tick() on snapshot arrival
+var _current_zone: String = ""           # D-073 (#529): zone tracking for ambient crossfades
+
+const LISTENING_FOCUS_TICKS: int = 30  # D-071: stationary ticks before ListeningFocus boost activates
 
 func _ready() -> void:
 	print("The Settled Reach — client initialized")
@@ -128,6 +132,13 @@ func _process(_delta: float) -> void:
 		# D-018 #125: Play close-range sound events via positional 2D audio
 		_play_close_sound_events()
 
+		# D-073 (#529): Zone ambient crossfade — detect player tile zone, trigger set_zone on change.
+		_update_zone()
+
+		# D-071 (#530): ListeningFocus boost — stationary 30+ ticks boosts WorldSFX.
+		# Only activates when no dialogue/confrontation dip is active (D-070).
+		_update_listening_focus()
+
 		# Show monologue if server sent one this tick (#414)
 		_consume_monologue()
 
@@ -162,6 +173,14 @@ func _process(_delta: float) -> void:
 			if bug_report_dialog and not bug_report_dialog.is_active():
 				bug_report_dialog.start_capture()
 			continue
+		# #528: ESC/OPEN_MENU — client-only, toggle audio settings dialog
+		if input.action == InputMapper.Action.OPEN_MENU:
+			if settings_dialog:
+				if settings_dialog.is_open():
+					settings_dialog.close()
+				else:
+					settings_dialog.open()
+			continue
 		if input.action == InputMapper.Action.INTERACT:
 			# D-057: prefer interaction list (multi-verb), fall back to prompt (v0.1)
 			var target_id: int = -1
@@ -235,6 +254,38 @@ func _play_recognition_chimes() -> void:
 			_known_recognition_ids.erase(eid)
 
 
+# D-073 (#529): Zone ambient crossfade — read zone_id from player's current tile.
+# Calls AudioManager.set_zone() when zone changes (AudioManager handles crossfade).
+# zone_id field is server-authoritative; missing field treated as empty (no zone).
+func _update_zone() -> void:
+	var px := int(GameState.player_position.x)
+	var py := int(GameState.player_position.y)
+	var zone: String = ""
+	for tile in GameState.visible_tiles:
+		if not tile is Dictionary:
+			continue
+		if tile.get("x") == px and tile.get("y") == py:
+			zone = tile.get("zone_id", "")
+			break
+	if zone != _current_zone:
+		_current_zone = zone
+		AudioManager.set_zone(zone)
+
+
+# D-071 (#530): ListeningFocus boost — World SFX +2.5dB when stationary 30+ ticks.
+# Uses AudioManager.get_active_dip() as single source of truth (no separate flag).
+# Only activates when no other dip (dialogue/confrontation) is running.
+# Only deactivates its own dip — never touches dialogue/confrontation.
+# D-070: no UI indicator — the boost is "felt, not computed."
+func _update_listening_focus() -> void:
+	var current_dip := AudioManager.get_active_dip()
+	var threshold_met := GameState.stationary_ticks >= LISTENING_FOCUS_TICKS
+	if threshold_met and current_dip == "":
+		AudioManager.apply_dip("listening_focus")
+	elif not threshold_met and current_dip == "listening_focus":
+		AudioManager.clear_dip()
+
+
 # Consume-once per tick: show monologue text, then clear.
 # Tick guard prevents re-triggering when the same tick is polled multiple
 # times (client FPS > sim tick rate).