Fix restart revision bump and separator DPR scaling

Two small correctness fixes from PR review:

- When the simulation restarts (totalFrames drops), bump the revision
  counter immediately so React re-renders to pick up the empty store.
  Previously the bump only happened when subsequent fetched frames
  were pushed, so a cancelled/empty follow-up fetch left the chart
  displaying stale pre-restart data.

- In the drawClear hook, scale the separator line's width and its
  sub-pixel offset by devicePixelRatio. uPlot's canvas uses physical
  pixels, so the previous hardcoded 1/0.5 values rendered at 0.5/0.25
  CSS pixels on HiDPI displays — thinner than uPlot's own grid lines.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kube

libs/@hashintel/petrinaut/src/views/Editor/panels/BottomPanel/subviews/simulation-timeline.tsx

@@ -222,6 +222,7 @@ function useStreamingData(): {
       if (totalFrames < processedRef.current) {
         storeRef.current = createEmptyStore(store.places);
         processedRef.current = 0;
+        setRevision((r) => r + 1);
       }
 
       const startIndex = processedRef.current;
@@ -680,12 +681,13 @@ function buildUPlotOptions(opts: ChartOptions): uPlot.Options {
         (u) => {
           const { ctx } = u;
           const { left: bx, width: bw, top: by } = u.bbox;
+          const dpr = devicePixelRatio;
           ctx.save();
           ctx.strokeStyle = "#cbd5e1";
-          ctx.lineWidth = 1;
+          ctx.lineWidth = dpr;
           ctx.beginPath();
-          ctx.moveTo(bx, by - 0.5);
-          ctx.lineTo(bx + bw, by - 0.5);
+          ctx.moveTo(bx, by - 0.5 * dpr);
+          ctx.lineTo(bx + bw, by - 0.5 * dpr);
           ctx.stroke();
           ctx.restore();
         },