ui: stop the scope label colliding with the time-axis labels

The "Waveform (Time/Amplitude)" label was drawn in the same ~30px band as
the time-axis labels and the horizontal scrollbar, so it overlapped the
"0.0s / 7.7s / ..." ticks. Shorten to "Waveform" and tuck it faded inside
the scope's top-left, clear of that band.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/spectrogram.c

@@ -960,8 +960,10 @@ int main(int argc, char* argv[])
                 } else {
                     DrawScopeView(&app.scopeView, -1.0f);
                 }
-                // Draw scope label
-                DrawTextScaled("Waveform (Time/Amplitude)", viewBounds.x, app.scopeView.y - 20, 14, LIGHTGRAY);
+                // Scope label, tucked inside the top-left so it clears the time
+                // axis labels and scrollbar that sit in the band above the scope.
+                DrawTextScaled("Waveform", viewBounds.x + 4 * renderScale, app.scopeView.y + 3 * renderScale,
+                               11, Fade(LIGHTGRAY, 0.5f));
             }
             
             // Draw divider line + handle. Always shown (even when the scope is