soundd: mix ClearPilot ding alongside alerts; add ding.wav

Adds the ding sound effect that fires on speed-limit changes / cruise-
warning transitions (writers will set ClearpilotPlayDing="1" in
/dev/shm/params; soundd polls at ~2Hz, clears the flag, plays once).

The ding plays at MAX_VOLUME independent of the alert volume map and
mixes into the same output stream. Single-shot — no looping. Loaded
once at startup; failure to load just disables the ding (rest of soundd
keeps working).

print-to-stderr, not cloudlog (CLAUDE.md rule).

selfdrive/ui/soundd.py

@@ -93,6 +93,29 @@ class Soundd:
 
     self.spl_filter_weighted = FirstOrderFilter(0, 2.5, FILTER_DT, initialized=False)
 
+    # CLEARPILOT ding (plays independently of alerts; triggered by writers
+    # setting ClearpilotPlayDing="1" in /dev/shm/params).
+    self.ding_sound = None
+    self.ding_frame = 0
+    self.ding_playing = False
+    self.ding_check_counter = 0
+    self._load_ding()
+
+  def _load_ding(self):
+    import sys
+    ding_path = BASEDIR + "/selfdrive/clearpilot/sounds/ding.wav"
+    try:
+      wavefile = wave.open(ding_path, 'r')
+      assert wavefile.getnchannels() == 1
+      assert wavefile.getsampwidth() == 2
+      assert wavefile.getframerate() == SAMPLE_RATE
+      length = wavefile.getnframes()
+      self.ding_sound = np.frombuffer(wavefile.readframes(length), dtype=np.int16).astype(np.float32) / (2**16/2)
+      print(f"CLP soundd: ClearPilot ding loaded: {length} frames", file=sys.stderr, flush=True)
+    except Exception as e:
+      print(f"CLP soundd: failed to load ding sound: {e}", file=sys.stderr, flush=True)
+      self.ding_sound = None
+
   def load_sounds(self):
     self.loaded_sounds: dict[int, np.ndarray] = {}
 
@@ -137,7 +160,20 @@ class Soundd:
         written_frames += frames_to_write
         self.current_sound_frame += frames_to_write
 
-    return ret * self.current_volume
+    ret = ret * self.current_volume
+
+    # CLEARPILOT: mix in ding (independent of alerts, always max volume)
+    if self.ding_playing and self.ding_sound is not None:
+      ding_remaining = len(self.ding_sound) - self.ding_frame
+      if ding_remaining > 0:
+        frames_to_write = min(ding_remaining, frames)
+        ret[:frames_to_write] += self.ding_sound[self.ding_frame:self.ding_frame + frames_to_write] * MAX_VOLUME
+        self.ding_frame += frames_to_write
+      else:
+        self.ding_playing = False
+        self.ding_frame = 0
+
+    return ret
 
   def callback(self, data_out: np.ndarray, frames: int, time, status) -> None:
     if status:
@@ -205,6 +241,14 @@ class Soundd:
         if self.params_memory.get_bool("FrogPilotTogglesUpdated"):
           self.update_frogpilot_params()
 
+        # CLEARPILOT: poll ClearpilotPlayDing at ~2Hz; clear it on read.
+        self.ding_check_counter += 1
+        if self.ding_check_counter % 10 == 0 and self.ding_sound is not None:
+          if self.params_memory.get("ClearpilotPlayDing") == b"1":
+            self.params_memory.put("ClearpilotPlayDing", "0")
+            self.ding_playing = True
+            self.ding_frame = 0
+
   def update_frogpilot_params(self):
     self.alert_volume_control = self.params.get_bool("AlertVolumeControl")