feat(audio): move beat routing server-side and extend presets

Route beat-triggered manual selects from the controller server, add preset background and beat-counter UI support, and bump led-driver to include the matching pattern/runtime fixes.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/make_bpm_test_audio.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+"""Generate a click-track WAV file at a known BPM.
+
+Example:
+  python tests/make_bpm_test_audio.py --bpm 128 --seconds 60 --output tests/audio_128bpm.wav
+"""
+
+from __future__ import annotations
+
+import argparse
+import math
+import struct
+import wave
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(description="Generate known-BPM click track")
+    parser.add_argument("--bpm", type=float, required=True, help="Target BPM (e.g. 120)")
+    parser.add_argument("--seconds", type=float, default=30.0, help="Audio duration in seconds")
+    parser.add_argument("--sample-rate", type=int, default=44100, help="Sample rate")
+    parser.add_argument("--click-ms", type=float, default=25.0, help="Click length in milliseconds")
+    parser.add_argument(
+        "--output",
+        default="tests/bpm_test.wav",
+        help="Output WAV path",
+    )
+    return parser.parse_args()
+
+
+def main() -> int:
+    args = parse_args()
+    if args.bpm <= 0:
+        raise SystemExit("--bpm must be > 0")
+    if args.seconds <= 0:
+        raise SystemExit("--seconds must be > 0")
+
+    sample_rate = int(args.sample_rate)
+    total_samples = int(args.seconds * sample_rate)
+    beat_interval = 60.0 / float(args.bpm)
+    click_samples = max(1, int((args.click_ms / 1000.0) * sample_rate))
+
+    data = [0.0] * total_samples
+    beat_index = 0
+    t = 0.0
+    while t < args.seconds:
+        start = int(t * sample_rate)
+        # Slight accent every 4 beats to help human counting.
+        freq = 1760.0 if beat_index % 4 == 0 else 1320.0
+        amp = 0.9 if beat_index % 4 == 0 else 0.6
+        for i in range(click_samples):
+            idx = start + i
+            if idx >= total_samples:
+                break
+            env = math.exp(-8.0 * (i / click_samples))
+            s = amp * env * math.sin((2.0 * math.pi * freq * i) / sample_rate)
+            data[idx] += s
+        t += beat_interval
+        beat_index += 1
+
+    with wave.open(args.output, "wb") as wf:
+        wf.setnchannels(1)
+        wf.setsampwidth(2)
+        wf.setframerate(sample_rate)
+        frames = bytearray()
+        for s in data:
+            clipped = max(-1.0, min(1.0, s))
+            frames.extend(struct.pack("<h", int(clipped * 32767)))
+        wf.writeframes(bytes(frames))
+
+    print(f"Wrote {args.output} at {args.bpm:.2f} BPM for {args.seconds:.1f}s")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())