fix(client): address PR #47 review — murmur deferral, zone extraction, 6 tests

Remove premature Voice/VoiceConversation from SOUND_EVENT_ASSETS (D-072
defers murmur to end-to-end sprint). Extract current_zone_id in
GameState.apply_snapshot() as first-class field, eliminating O(N) tile
scan in main.gd (D-020 server-authoritative). Add dir.list_dir_end()
after registry scan. Add rapid zone-crossing + _load_prefs() roundtrip
tests. Enhance comments on hub/workplace same-asset pattern, station
base hum, and confrontation dip replacement semantics.

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

client/scripts/autoloads/audio_manager.gd

@@ -45,7 +45,12 @@ const FILTER_CUTOFF_DEFAULT := 20500.0
 const CROSSFADE_DURATION := 1.8  # D-073: 1.5-2s spec, mid-range
 
 # Maps server zone_id strings to ambient asset keys (filenames in res://audio/).
-# Hub and Workplace share the same ambient layer — same location type.
+# Hub and Workplace intentionally share the same ambient layer (amb_hub_layer) —
+# they are the same location type, so hub→workplace transition is a same-asset no-op
+# (old_asset != new_asset guard skips the fade-out). Sprint brief consolidates
+# D-038's "amb_workplace_layer" to "amb_hub_layer" for v0.1.
+# Note: amb_station_base (D-038 global base hum) plays globally via play_loop()
+# at startup — it is not zone-dependent and has no ZONE_ASSETS entry.
 const ZONE_ASSETS: Dictionary = {
 	"hub":       "amb_hub_layer",
 	"workplace": "amb_hub_layer",
@@ -129,6 +134,7 @@ func _scan_dir(path: String) -> void:
 				if stream:
 					_registry[file_name.get_basename()] = stream
 		file_name = dir.get_next()
+	dir.list_dir_end()
 
 
 func has_asset(asset_key: String) -> bool:
@@ -201,10 +207,6 @@ const SOUND_EVENT_ASSETS: Dictionary = {
 	"FootstepCrouch": "sfx_footstep_metal_walk",  # D-053: same asset until stance-differentiated audio lands
 	"FootstepSprint": "sfx_footstep_metal_run",
 	"FootstepRun":    "sfx_footstep_metal_run",
-	# D-072 (#533): NPC conversation murmur — single universal asset, World SFX bus.
-	# Zone ambient provides natural conspicuousness (bar buries it, corridor exposes it).
-	"Voice":          "sfx_npc_murmur",
-	"VoiceConversation": "sfx_npc_murmur",
 }
 
 

client/scripts/autoloads/game_state.gd

@@ -68,6 +68,11 @@ var close_sound_events: Array = []
 var stationary_ticks: int = 0
 var _prev_player_position: Vector2 = Vector2(-1e9, -1e9)  # sentinel: no previous position
 
+# D-073 (#529): Server-authoritative zone_id from the player's current tile.
+# Extracted in apply_snapshot() — avoids O(N) tile scan in main.gd per Tyre review.
+# Empty string when zone_id field absent (server hasn't shipped OQ-09 yet).
+var current_zone_id: String = ""
+
 func apply_snapshot(snapshot: Dictionary) -> void:
 	current_snapshot = snapshot
 
@@ -197,6 +202,17 @@ func apply_snapshot(snapshot: Dictionary) -> void:
 		medium_sound_events = []
 		close_sound_events = []
 
+	# D-073 (#529): Extract zone_id from the player's current tile (server-authoritative).
+	# O(1) via visible_positions dict would be ideal, but tiles are arrays without
+	# positional indexing — use the same tile iteration below instead.
+	current_zone_id = ""
+	var _px := int(player_position.x)
+	var _py := int(player_position.y)
+	for _ztile in visible_tiles:
+		if _ztile is Dictionary and _ztile.get("x") == _px and _ztile.get("y") == _py:
+			current_zone_id = _ztile.get("zone_id", "")
+			break
+
 	# v2: visible_tiles with visibility sectors
 	# Derives visible_positions when not explicitly provided (real server mode)
 	if snapshot.has("visible_tiles") and snapshot.visible_tiles is Array and snapshot.visible_tiles.size() > 0:

client/scripts/main.gd

@@ -254,19 +254,11 @@ func _play_recognition_chimes() -> void:
 			_known_recognition_ids.erase(eid)
 
 
-# D-073 (#529): Zone ambient crossfade — read zone_id from player's current tile.
+# D-073 (#529): Zone ambient crossfade — reads zone_id from GameState.current_zone_id
+# (extracted in apply_snapshot(), server-authoritative per D-020).
 # 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
+	var zone := GameState.current_zone_id
 	if zone != _current_zone:
 		_current_zone = zone
 		AudioManager.set_zone(zone)