fix: switch from RMS to peak detection for more accurate level meters

Changed level calculation from RMS to peak detection to show
more realistic and responsive meter values.

The Problem:
- RMS calculation produced values typically in 0-30% range
- Audio signals have low average RMS (0.1-0.3 for music)
- Meters appeared broken, never reaching higher levels

The Solution:
- Switched to peak detection (max absolute value)
- Peaks now properly show 0-100% range
- More responsive to transients and dynamics
- Matches typical DAW meter behavior

Algorithm Change:
Before (RMS):
  rms = sqrt(sum(normalized²) / length)

After (Peak):
  peak = max(abs(normalized))

Applied to Both:
- Recording input level monitoring (useRecording)
- Playback output level monitoring (useMultiTrackPlayer)

Benefits:
✅ Full 0-100% range utilization
✅ More responsive visual feedback
✅ Accurate representation of audio peaks
✅ Consistent with professional audio software

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/hooks/useMultiTrackPlayer.ts

@@ -64,14 +64,16 @@ export function useMultiTrackPlayer(tracks: Track[], masterVolume: number = 1) {
       const dataArray = new Uint8Array(analyser.frequencyBinCount);
       analyser.getByteTimeDomainData(dataArray);
 
-      // Calculate RMS level
-      let sum = 0;
+      // Calculate peak level (more responsive than RMS for visual meters)
+      let peak = 0;
       for (let i = 0; i < dataArray.length; i++) {
-        const normalized = (dataArray[i] - 128) / 128;
-        sum += normalized * normalized;
+        const normalized = Math.abs((dataArray[i] - 128) / 128);
+        if (normalized > peak) {
+          peak = normalized;
+        }
       }
-      const rms = Math.sqrt(sum / dataArray.length);
-      levels[track.id] = rms;
+
+      levels[track.id] = peak;
     });
 
     setTrackLevels(levels);

lib/hooks/useRecording.ts

@@ -78,15 +78,16 @@ export function useRecording(): UseRecordingReturn {
 
       analyser.getByteTimeDomainData(dataArray);
 
-      // Calculate RMS level
-      let sum = 0;
+      // Calculate peak level (more responsive than RMS for visual meters)
+      let peak = 0;
       for (let i = 0; i < dataArray.length; i++) {
-        const normalized = (dataArray[i] - 128) / 128;
-        sum += normalized * normalized;
+        const normalized = Math.abs((dataArray[i] - 128) / 128);
+        if (normalized > peak) {
+          peak = normalized;
+        }
       }
-      const rms = Math.sqrt(sum / dataArray.length);
 
-      setState((prev) => ({ ...prev, inputLevel: rms }));
+      setState((prev) => ({ ...prev, inputLevel: peak }));
 
       animationFrameRef.current = requestAnimationFrame(updateLevel);
     };