Phase 17/18 closure: stockpile filter UI + day summary + atmospheric audio

Three-agent fan-out (gdscript-refactor x3) closing deferred polish:

- Stockpile chip filter UI: new StockpilePanel (layer 18, right-anchored,
  mirrors WorkbenchPanel). 5-priority segmented control + 21-chip 4-col
  filter grid using Item.ALL_TYPES; wildcard (empty accepted_types) shows
  all chips checked with 'All' hint, first explicit pick switches to
  explicit-list mode. Selection chain extended to pawn → workbench →
  stockpile with mutual exclusion. 12 ui.stockpile.* + 13 item.* keys.

- DaySummaryCard: layer-19 modal auto-opens at dusk→night via day_ended,
  auto-pauses sim, shows day+season header, weather row, stats grid with
  green/yellow/red tension bar, Continue dismiss + backdrop tap.
  Settings 'Show end-of-day summary' toggle persists via GameState.

- Atmospheric audio: rain ambient loop (Cozy Melodies Pack 6) on
  weather_changed rain/storm with 0.5s fade-out on clear; thunder sting
  (Magic and Spells 6) on rain→storm transition; raid warning sting
  (Sword Pack 1, 'blades drawn') on EventBus.wolf_spawned. All on SFX
  bus — inherits existing slider + suspend mute.

Contracts pre-written before fan-out: EventBus.stockpile_selected /
stockpile_deselected / wolf_spawned signals; WolfSpawner._trigger_raid
+ _on_request_wolf_spawn now emit wolf_spawned with the spawned array.

MCP runtime verified: StockpilePanel opens with 21 chips, DaySummaryCard
renders weather row + tension bar + auto-pause, rain_player.playing=true
on weather_changed(rain), all three new SFX keys in Audio.SFX_FILES.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

autoload/audio.gd

@@ -1,5 +1,5 @@
 extends Node
-## AudioManager — Phase 18.
+## AudioManager — Phase 18 + atmospheric audio (Phase 18 follow-up).
 ##
 ## Owns three AudioServer buses (Master, Music, SFX), a small catalog of music
 ## loops + one-shot SFX, and a single AudioStreamPlayer for the music director.
@@ -9,6 +9,13 @@ extends Node
 ## EventBus signals (combat, storyteller stings) and direct calls from Tree /
 ## Rock entities for chop / mine completion sounds.
 ##
+## Atmospheric audio (Phase 18 follow-up):
+##   - Rain ambient loop: persistent AudioStreamPlayer on SFX bus, fades in/out
+##     on weather_changed. Routed to SFX bus (no new bus) so it respects the
+##     existing SFX slider and application-pause muting via Master bus mute.
+##   - Storm thunder sting: one-shot on WEATHER_RAIN → WEATHER_STORM transition.
+##   - Raid warning sting: one-shot on wolf_spawned.
+##
 ## Volume sliders in SettingsMenu drive set_*_db() at the Master/Music/SFX bus
 ## level. App-pause mutes everything (NOTIFICATION_APPLICATION_PAUSED / focus
 ## loss) to match the existing "no background simulation" rule.
@@ -33,6 +40,14 @@ const SFX_FILES: Dictionary = {
 	&"tree_fell": "res://audio/sfx/tree_fell.ogg",
 	&"mine_tick": "res://audio/sfx/mine_tick.ogg",
 	&"combat_hit": "res://audio/sfx/combat_hit.ogg",
+	# Atmospheric — Phase 18 follow-up.
+	# rain_ambient: Cozy Melodies Pack 6 (ElvGames Ultimate Farming RPG Tier 3)
+	&"rain_ambient": "res://audio/sfx/rain_ambient.ogg",
+	# thunder_sting: Magic and Spells 6 (ElvGames Ultimate Farming RPG Tier 3)
+	&"thunder_sting": "res://audio/sfx/thunder_sting.ogg",
+	# raid_warning: Sword Sound Effects Pack 1 (ElvGames Ultimate Farming RPG Tier 3)
+	# Sword unsheathe sting used as danger signal; no dedicated alarm/horn in bundle.
+	&"raid_warning": "res://audio/sfx/raid_warning.ogg",
 }
 
 const MUSIC_FILES: Dictionary = {
@@ -57,6 +72,14 @@ var master_linear: float = 1.0
 var music_linear: float = 1.0
 var sfx_linear: float = 1.0
 
+# Atmospheric — rain ambient loop player. Persistent; stream stays loaded.
+# Routed to SFX bus so it inherits the SFX slider and app-pause muting.
+var _rain_player: AudioStreamPlayer = null
+# Tween used for the rain fade-out (clear/cold_snap). Cancelled on re-rain.
+var _rain_tween: Tween = null
+# Track previous weather to detect RAIN → STORM transition for thunder sting.
+var _prev_weather: StringName = &""
+
 
 # ── lifecycle ───────────────────────────────────────────────────────────────
 
@@ -68,6 +91,15 @@ func _ready() -> void:
 	_music_player.name = "MusicPlayer"
 	add_child(_music_player)
 
+	# Rain ambient: persistent looping player on SFX bus. Starts silent; weather
+	# signal activates it. Routing to SFX bus means app-pause muting (Master bus)
+	# covers it automatically — no extra NOTIFICATION handling needed.
+	_rain_player = AudioStreamPlayer.new()
+	_rain_player.bus = BUS_SFX
+	_rain_player.name = "RainAmbientPlayer"
+	_rain_player.volume_db = 0.0
+	add_child(_rain_player)
+
 	# SFX → world event wiring. Keep this list short and obvious.
 	if EventBus.has_signal("pawn_took_damage"):
 		EventBus.pawn_took_damage.connect(_on_pawn_took_damage)
@@ -75,6 +107,10 @@ func _ready() -> void:
 		EventBus.storyteller_event_fired.connect(_on_storyteller_event_fired)
 	if EventBus.has_signal("alert_added"):
 		EventBus.alert_added.connect(_on_alert_added)
+	if EventBus.has_signal("weather_changed"):
+		EventBus.weather_changed.connect(_on_weather_changed)
+	if EventBus.has_signal("wolf_spawned"):
+		EventBus.wolf_spawned.connect(_on_wolf_spawned)
 
 	# Music director: swap day/night loops as Clock.phase_changed fires.
 	if Clock.has_signal("phase_changed"):
@@ -86,7 +122,14 @@ func _ready() -> void:
 		initial_phase = Clock.current_phase()
 	_apply_phase_to_music(initial_phase)
 
-	Audit.log("audio", "AudioManager ready (master/music/sfx buses online)")
+	# Sync rain loop to current weather in case we loaded mid-rain (e.g. after
+	# save/load). Weather autoload is ready before Audio in the autoload list;
+	# safe to query here.
+	if Weather.has_method("is_raining") and Weather.is_raining():
+		_prev_weather = Weather.current_weather
+		_start_rain_loop()
+
+	Audit.log("audio", "AudioManager ready (master/music/sfx buses online + atmospheric)")
 
 
 ## NOTIFICATION_APPLICATION_PAUSED fires when the app is suspended (mobile
@@ -232,3 +275,54 @@ func _on_alert_added(_severity: StringName, _text: String, _focus_tile: Vector2i
 
 func _on_clock_phase_changed(new_phase: StringName) -> void:
 	_apply_phase_to_music(new_phase)
+
+
+func _on_weather_changed(weather: StringName) -> void:
+	var prev: StringName = _prev_weather
+	_prev_weather = weather
+
+	match weather:
+		&"rain", &"storm":
+			# Cancel any pending fade-out tween.
+			if _rain_tween != null and _rain_tween.is_valid():
+				_rain_tween.kill()
+				_rain_tween = null
+			_start_rain_loop()
+			# Thunder sting only on a direct transition into storm.
+			if weather == &"storm" and prev != &"storm":
+				play_sfx(&"thunder_sting")
+		_:
+			# WEATHER_CLEAR or WEATHER_COLD_SNAP — fade out rain loop.
+			_stop_rain_loop_fade()
+
+
+func _on_wolf_spawned(wolves: Array) -> void:
+	if wolves.size() > 0:
+		play_sfx(&"raid_warning")
+
+
+# ── rain ambient helpers ─────────────────────────────────────────────────────
+
+func _start_rain_loop() -> void:
+	# Load the stream once and reuse across transitions.
+	var stream: AudioStream = _load_sfx(&"rain_ambient")
+	if stream == null:
+		return
+	if _rain_player.stream != stream:
+		_rain_player.stream = stream
+		if stream is AudioStreamOggVorbis:
+			stream.loop = true
+	_rain_player.volume_db = 0.0
+	if not _rain_player.playing:
+		_rain_player.play()
+
+
+func _stop_rain_loop_fade() -> void:
+	if not _rain_player.playing:
+		return
+	# 0.5 s linear fade from current volume to SILENT_DB, then stop.
+	if _rain_tween != null and _rain_tween.is_valid():
+		_rain_tween.kill()
+	_rain_tween = create_tween()
+	_rain_tween.tween_property(_rain_player, "volume_db", SILENT_DB, 0.5)
+	_rain_tween.tween_callback(_rain_player.stop)