[Bug] ECharts 6.1.0 canvas dirty-rect repaint corrupts dense line series on tooltip axis-pointer hover

### Version

6.1.0

### Link to Minimal Reproduction

https://codesandbox.io/p/sandbox/tender-merkle-ymcjr9?file=%2Fsrc%2Findex.js%3A4%2C51

### Steps to Reproduce

Steps to Reproduce

Open the ECharts examples editor: https://echarts.apache.org/examples/en/editor.html
Paste the minimal reproduction snippet.
Ensure the page is running ECharts 6.1.0.
Keep useDirtyRect: true.
Hover/move the mouse across the chart so the tooltip axis pointer updates.

### Current Behavior

When hovering the chart, parts of the dense line series visually disappear or render as broken/dashed segments. The underlying data is still present, and the tooltip continues to resolve values, but the canvas repaint appears corrupted around axis-pointer updates.

The issue disappears when either:

useDirtyRect is set to false
the tooltip axis pointer is disabled

### Expected Behavior

Hovering should only update the tooltip and axis pointer. The line series should remain visually continuous and unchanged while the pointer moves.

### Environment

```markdown
- OS: OSX
- Browser: ALL
- Framework: ANgular
```

### Any additional comments?

This appears to be a regression in ECharts 6.1.0. The same chart behavior worked with ECharts 6.0.0.

The affected setup uses:

canvas renderer
useDirtyRect: true
dense line series
showSymbol: false
progressive rendering
visualMap piecewise coloring
tooltip with trigger: 'axis'
tooltip axisPointer.type: 'line'
For our app, disabling dirty rect hurts performance, and disabling the axis pointer removes useful chart feedback, so neither is a good long-term workaround.