Fix waveform: tick-based rendering + always-follow auto-scroll

- timeStep increments by 1 per tick (not by simSpeed ms)
- waveZoom = pixels per step directly (zoom changes wave width)
- Speed control only changes real-time interval between ticks
- Auto-scroll always follows latest data regardless of zoom level

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

js/waveform.js

@@ -132,9 +132,8 @@ export function drawWaveforms() {
     // Visible width in steps
     const visibleSteps = wc.width / pxPerStep;
 
-    // Auto-scroll to show latest (only if near the end)
-    const isNearEnd = state.waveScroll >= state.timeStep - visibleSteps - 2;
-    if (totalPx > wc.width && isNearEnd) {
+    // Auto-scroll: always follow the latest data
+    if (totalPx > wc.width) {
         state.waveScroll = state.timeStep - visibleSteps;
     }
     state.waveScroll = Math.max(0, state.waveScroll);