fix(nitro): support Valibot schemas

[onmax]

🔗 Linked issue

Resolves #313

📚 Description

The Nitro v3 package accepts raw Valibot schemas, but they do not expose Standard JSON Schema. This caused tools/list to return Valibot's internal schema and left prompt arguments empty.

This wraps raw Valibot schemas with the official converter before they reach h3-mcp. It covers tool inputs, tool outputs, and prompt arguments while preserving validation and transforms such as trim.

The converter is bundled into nitro-mcp-toolkit, so users do not need to install it.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly. No change was needed because this restores the documented Valibot support.

[vercel]

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[github-actions]

Thank you for following the naming conventions! 🙏

[pkg-pr-new]

npm i https://pkg.pr.new/nitro-mcp-toolkit@326

npm i https://pkg.pr.new/@nuxtjs/mcp-toolkit@326

commit: c56ff77