Implement NPC perception, returning trespassers, responder dispatch, wand screening, and accessibility polish

src/game/audio_feedback.gd

@@ -0,0 +1,60 @@
+class_name AudioFeedback
+extends Node
+## Procedural audio feedback (PLAN.md: Polish and Accessibility). Generates
+## short tones for confirmation prompts, radio responses, and escalation
+## feedback without requiring audio assets. Headless-safe: in headless mode
+## the AudioServer is a dummy and playback is a no-op.
+
+const SAMPLE_RATE := 22050.0
+
+var _players: Array[AudioStreamPlayer] = []
+
+func _ready() -> void:
+	# Pre-create a few players so overlapping cues don't cut each other off.
+	for i in 4:
+		var player := AudioStreamPlayer.new()
+		add_child(player)
+		_players.append(player)
+
+## Play a short confirmation beep (single high tone).
+func play_confirm() -> void:
+	_play_tone(880.0, 0.12, 0.5)
+
+## Play a radio-response cue (two quick tones).
+func play_radio_response() -> void:
+	_play_tone(660.0, 0.10, 0.5)
+	_play_tone(990.0, 0.10, 0.5, 0.12)
+
+## Play an escalation warning cue (low descending tone).
+func play_escalation(level: int) -> void:
+	var freq := 440.0 - float(level) * 40.0
+	_play_tone(maxf(freq, 180.0), 0.18, 0.6)
+
+## Play a denial/error cue (low buzz).
+func play_deny() -> void:
+	_play_tone(220.0, 0.20, 0.5)
+
+## Generate a sine-wave tone and play it on a free player.
+func _play_tone(freq: float, duration: float, volume: float, delay: float = 0.0) -> void:
+	var player := _free_player()
+	if player == null:
+		return
+	var stream := AudioStreamGenerator.new()
+	stream.mix_rate = SAMPLE_RATE
+	stream.buffer_length = duration + 0.05
+	player.stream = stream
+	player.volume_db = linear_to_db(volume)
+	player.play()
+	# Fill the generator buffer with a sine wave.
+	var playback: AudioStreamGeneratorPlayback = player.get_stream_playback()
+	var frames := int(SAMPLE_RATE * duration)
+	for i in frames:
+		var t := float(i) / SAMPLE_RATE
+		var sample := sin(TAU * freq * t) * 0.6
+		playback.push_frame(Vector2(sample, sample))
+
+func _free_player() -> AudioStreamPlayer:
+	for player in _players:
+		if not player.playing:
+			return player
+	return _players[0]