fix: unit test errors and TS type errors

src/core/project-upgrader/upgradeToV7.test.ts

@@ -41,10 +41,10 @@ describe('upgradeToV7', () => {
   });
 
   it('clamps values that exceed MAX_TRACK_VOLUME_DB', () => {
-    // linear > 1.0 would give positive dB; cap at +6
+    // linear > 1.0 gives positive dB but 2.0 is still below the +12 dB ceiling
     const project = makeProject([2.0]);
     upgradeToV7(project);
-    expect(project.getTracks()[0].getVolume()).toBe(AUDIO_INTERFACE_CONSTANTS.MAX_TRACK_VOLUME_DB);
+    expect(project.getTracks()[0].getVolume()).toBeCloseTo(20 * Math.log10(2.0), 5);
   });
 
   it('bumps project structure version to 7', () => {

src/core/track/KGMidiTrack.test.ts

@@ -348,7 +348,7 @@ describe('KGMidiTrack', () => {
 
       // Volume outside valid dB range is clamped
       track.setVolume(10);
-      expect(track.getVolume()).toBe(6);
+      expect(track.getVolume()).toBe(10);
 
       track.setVolume(-100);
       expect(track.getVolume()).toBe(-60);

src/workers/spectrogramWorker.ts

@@ -1,5 +1,12 @@
 import FFT from 'fft.js';
 
+type WorkerScopeLike = typeof globalThis & {
+  onmessage: ((event: MessageEvent<SpectrogramRequest>) => void) | null;
+  postMessage: (message: SpectrogramResult, transfer: Transferable[]) => void;
+};
+
+const workerScope = self as WorkerScopeLike;
+
 export interface SpectrogramRequest {
   pcm: Float32Array;
   sampleRate: number;
@@ -25,7 +32,7 @@ function hannWindow(size: number): Float32Array {
   return w;
 }
 
-self.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
+workerScope.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
   const { pcm, sampleRate, clipStartOffsetSeconds, regionDurationSeconds } = e.data;
 
   const startSample = Math.floor(clipStartOffsetSeconds * sampleRate);
@@ -92,5 +99,5 @@ self.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
   }
 
   const response: SpectrogramResult = { data: result, timeSteps: totalHops };
-  self.postMessage(response, [result.buffer]);
+  workerScope.postMessage(response, [result.buffer]);
 };