Touch line goes through the highest point

**Describe the bug**
The touchline of the line chart, when having 2+ lines goes through the highest points overlaying it, when
`getTouchLineEnd: (data, index) => double.infinity`.
I think it should be the same as for the lower point, when it just going through it, but not overlaying (see screenshot)

**To Reproduce**
Provide us a completely reproducible code (contains the main function) in a `main.dart` file, it helps us to find the bug immediately.

**Screenshots**

**Versions**
- which version of the Flutter are you using?
Flutter 3.32.1 • channel stable • https://github.com/flutter/flutter.git
Framework • revision b25305a883 (3 weeks ago) • 2025-05-29 10:40:06 -0700
Engine • revision 1425e5e9ec (3 weeks ago) • 2025-05-28 14:26:27 -0700
Tools • Dart 3.8.1 • DevTools 2.45.1

- which version of the FlChart are you using?
version: "1.0.0"

Create the requested reproducible main.dart example with a line chart containing 2+ lines and getTouchLineEnd returning double.infinity. Run it with Flutter 3.32.1 and fl_chart 1.0.0, then compare the touchline at the highest points with the lower-point behavior shown in the screenshot; done means the line no longer overlays the highest points.

Written by the indexing model from the issue text.