fix: moasic chart's crosshair can not render rect shape

[kkxxkk2019]

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[Copilot]

Pull request overview

Fixes crosshair rect rendering for mosaic-like (reversed start/end) continuous data ranges by normalizing range comparisons and positioning.

Changes:

• Update getDatumByValue to match values within a range regardless of whether startField is less than or greater than endField.
• Adjust cartesian crosshair layout logic to anchor coord at the left edge of a continuous range band (using Math.min(posStart, posEnd)).
• Add unit tests covering reversed-field range lookup and rect crosshair layout behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
packages/vchart/src/component/crosshair/utils/common.ts	Makes datum lookup range-direction agnostic via min/max bounds.
packages/vchart/src/component/crosshair/utils/cartesian.ts	Fixes continuous range band positioning so rect crosshair spans the expected interval (incl. mosaic).
packages/vchart/__tests__/unit/component/crosshair/crosshair-util.test.ts	Adds unit coverage for reversed ranges and rect layout/clamping behavior.

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[Copilot]

When field2 exists and the underlying data uses reversed start/end fields (e.g. mosaic where field1 can be the larger bound), the label text ${datum[field1]} ~ ${datum[field2]} will render in reversed order (e.g. 0.6 ~ 0.2). Since coord is normalized with Math.min(posStart, posEnd), consider also normalizing the displayed range to ascending order (based on the datum values) so the crosshair label matches the visual rect direction.

Suggested change

	bandSize = Math.abs(posStart - posEnd);
	coord = Math.min(posStart, posEnd);
	value = `${datum[field1]} ~ ${datum[field2]}`;
	const startValue = datum[field1];
	const endValue = datum[field2];
	const [rangeStartValue, rangeEndValue] =
	startValue <= endValue ? [startValue, endValue] : [endValue, startValue];
	bandSize = Math.abs(posStart - posEnd);
	coord = Math.min(posStart, posEnd);
	value = `${rangeStartValue} ~ ${rangeEndValue}`;

[xuefei1313]

自动 Review（机器人）：

• 关注点：本次 PR 为修复 Mosaic 图的 crosshair 渲染（rect 形状）。
• 建议自查：
  1. 是否新增/更新了对应的 demo 或单测，覆盖 rect/line 等不同形状；
  2. crosshair 在不同主题/缩放/高清屏下的边界与对齐；
  3. 是否影响 tooltip / axis pointer 等相关交互；
• 请以 CI 结果为准，如 CI 全绿且本地验证通过，可考虑合入。

（本评论为自动化提示，不代替人工 Review）