Add theme property to Icon schema

[DaleSeo]

This PR adds the missing theme property to IconSchema to bring the TypeScript SDK into full compliance with the MCP specification (2025-11-25).

Motivation and Context

The MCP specification defines an optional theme property on the Icon interface to indicate whether an icon is designed for light or dark backgrounds. While the SDK's spec.types.ts (auto-generated from the MCP spec) correctly includes theme?: "light" | "dark" on the Icon interface, the IconSchema in types.ts used for Zod validation was missing this property.

How Has This Been Tested?

No type errors from running npm run typecheck

Breaking Changes

None. This is a non-breaking additive change:

• The theme property is optional, so existing code continues to work
• Icons without a theme specified will pass validation as before
• Servers can now optionally include theme: "light" or theme: "dark" in their icon definitions

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/sdk@1290

commit: 911f353