fix(components): [collapse-transition] collapse get el exists height

[Innei]

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Description

🤖 Generated by Copilot at ff5b1b3

The pull request enhances the el-collapse-transition component by using the element's height and requestAnimationFrame for smoother transitions. It also updates the docs/examples/transitions/collapse.vue file to show the component's behavior with different content heights.

Related Issue

The problem I found when repairing affine.pro UI toeverything/AFFiNE.pro#112

Explanation of Changes

🤖 Generated by Copilot at ff5b1b3

• Improve el-collapse-transition component to handle elements with fixed or min-height (link, link)
  • Store existing height in data attribute before transition starts (link)
  • Use requestAnimationFrame and stored height to set maxHeight in enter hook (link)
• Adjust height of div element and content in collapse.vue example to demonstrate transition effect better (link)
  • Remove height from div element to allow el-collapse-transition to expand and collapse (link)
  • Add style attribute to v-show directive to set content height to 400px (link)

[pull-request-triage]

👋 @Innei, seems like this is your first time contribution to element-plus.

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• You can comment with /label Components:[component_name] to add a label for which component you are working on.
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[github-actions]

[github-actions]

Hello @Innei, thank you for contributing to element-plus, please see our guideline to see how to make contribution

[github-actions]

🧪 Playground Preview: https://element-plus.run/?pr=14801
Please comment the example via this playground if needed.

[Innei]

/label Components:collapse-transition

[btea]

Thank you for your contribution!