feat: speed limit ding sound when cruise warning sign appears

Plays a ding via soundd when the cruise warning sign becomes visible
(cruise set speed out of range vs speed limit) or when the speed limit
changes while the warning sign is already showing. Max 1 ding per 30s.

Ding is mixed independently into soundd output at max volume without
interrupting alert sounds. bench_cmd ding available for manual trigger.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

selfdrive/ui/soundd.py

@@ -93,6 +93,27 @@ class Soundd:
 
     self.spl_filter_weighted = FirstOrderFilter(0, 2.5, FILTER_DT, initialized=False)
 
+    # ClearPilot ding (plays independently of alerts)
+    self.ding_sound = None
+    self.ding_frame = 0
+    self.ding_playing = False
+    self.ding_check_counter = 0
+    self._load_ding()
+
+  def _load_ding(self):
+    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)
+      cloudlog.info(f"ClearPilot ding loaded: {length} frames")
+    except Exception as e:
+      cloudlog.error(f"Failed to load ding sound: {e}")
+      self.ding_sound = None
+
   def load_sounds(self):
     self.loaded_sounds: dict[int, np.ndarray] = {}
 
@@ -137,7 +158,20 @@ class Soundd:
         written_frames += frames_to_write
         self.current_sound_frame += frames_to_write
 
-    return ret * self.current_volume
+    ret = ret * self.current_volume
+
+    # Mix in ClearPilot 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:
@@ -197,6 +231,14 @@ class Soundd:
 
         self.get_audible_alert(sm)
 
+        # ClearPilot: check for ding trigger at ~2Hz
+        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
+
         rk.keep_time()
 
         assert stream.active