feat: Add LFO mode options to oscilloscope demo

- Add --lfo flag for slow modulation (0.5Hz)
- Add --fast-lfo flag for rhythmic modulation (5Hz)
- Display frequency type (LFO/Audio) in output
- More intuitive LFO usage for modulation applications

Usage:
  uv run python scripts/demo_oscilloscope.py --lfo --waveform sine
  uv run python scripts/demo_oscilloscope.py --fast-lfo --waveform triangle

scripts/demo_oscilloscope.py

@@ -116,7 +116,12 @@ def demo_oscilloscope(
     frames: int = 0,
 ):
     """Run oscilloscope demo."""
-    print(f"Oscilloscope demo: {waveform} wave at {frequency}Hz")
+    # Determine if this is LFO range
+    is_lfo = frequency <= 20.0 and frequency >= 0.1
+    freq_type = "LFO" if is_lfo else "Audio"
+
+    print(f"Oscilloscope demo: {waveform} wave")
+    print(f"Frequency: {frequency}Hz ({freq_type} range)")
     if frames > 0:
         print(f"Running for {frames} frames")
     else:
@@ -164,7 +169,17 @@ if __name__ == "__main__":
         "--frequency",
         type=float,
         default=1.0,
-        help="Oscillator frequency in Hz",
+        help="Oscillator frequency in Hz (LFO: 0.1-20Hz, Audio: >20Hz)",
+    )
+    parser.add_argument(
+        "--lfo",
+        action="store_true",
+        help="Use LFO frequency (0.5Hz - slow modulation)",
+    )
+    parser.add_argument(
+        "--fast-lfo",
+        action="store_true",
+        help="Use fast LFO frequency (5Hz - rhythmic modulation)",
     )
     parser.add_argument(
         "--frames",
@@ -174,8 +189,16 @@ if __name__ == "__main__":
     )
 
     args = parser.parse_args()
+
+    # Determine frequency based on mode
+    frequency = args.frequency
+    if args.lfo:
+        frequency = 0.5  # Slow LFO for modulation
+    elif args.fast_lfo:
+        frequency = 5.0  # Fast LFO for rhythmic modulation
+
     demo_oscilloscope(
         waveform=args.waveform,
-        frequency=args.frequency,
+        frequency=frequency,
         frames=args.frames,
     )