docs: generate Skills page GitHub links from real skill paths

[Copilot]

Description

Skills data is loaded from .claude/skills, but the page hardcoded links to skills/{id}/SKILL.md, producing broken GitHub URLs for .claude-backed skills.
This change makes link generation path-driven instead of convention-assumed.

• Data model update (docs/data/skills.data.js)

  • Add skillPath as repository-relative SKILL.md path derived from the discovered file location.
  • Normalize separators for cross-platform URL correctness.

• Rendering update (docs/skills.vue)

  • Build GitHub href from skill.skillPath instead of skills/${skill.id}/SKILL.md.

- :href="`https://github.com/longbridge/gpui-component/tree/main/skills/${skill.id}/SKILL.md`"
+ :href="`https://github.com/longbridge/gpui-component/tree/main/${skill.skillPath}`"

Screenshot

Before	After
[Put Before Screenshot here]	[Put After Screenshot here]

Break Changes

None.

How to Test

1. Run:

   node --no-warnings -e "import('./docs/data/skills.data.js').then(async m => { const data = await m.default.load(); for (const s of data) console.log(JSON.stringify({ id: s.id, skillPath: s.skillPath, generatedHref: 'https://github.com/longbridge/gpui-component/tree/main/' + s.skillPath })); })"

2. Confirm gpui-component-dev resolves to:
   https://github.com/longbridge/gpui-component/tree/main/.claude/skills/gpui-component-dev/SKILL.md

Checklist

• I have read the CONTRIBUTING document and followed the guidelines.
• Reviewed the changes in this PR and confirmed AI generated code (If any) is accurate.
• Passed cargo run for story tests related to the changes.
• Tested macOS, Windows and Linux platforms performance (if the change is platform-specific)