fix(audio): zero-fill FFT buffer tail after partial frame read

When ReadNextFrame returns fewer samples than the buffer size, the tail
contains stale samples from the previous iteration, contaminating
frequency analysis. Add clear() call after the partial-frame copy to
zero-fill the tail, matching the pattern already used in Pass 2
(rendering).

Signed-off-by: Martin Wimpress <code@wimpress.io>

Author: flexiondotorg

internal/audio/analyzer.go

@@ -140,6 +140,9 @@ func AnalyzeAudio(filename string, progressCb ProgressCallback) (*Profile, error
 		// Shift buffer left by samplesPerFrame, append new samples
 		copy(fftBuffer, fftBuffer[samplesPerFrame:])
 		copy(fftBuffer[config.FFTSize-samplesPerFrame:], frameBuf[:nRead])
+		if nRead < samplesPerFrame {
+			clear(fftBuffer[config.FFTSize-samplesPerFrame+nRead:])
+		}
 	}
 
 	// Set actual frame count and duration