fix: move MCP SDK to peer dependencies

[agcty]

Summary

Move @modelcontextprotocol/sdk from direct dependencies to peer dependencies, allowing consumers to control their own MCP SDK version.

Problem

Currently, @modelcontextprotocol/sdk is pinned as a direct dependency ("^1.23.0"). This causes issues for consumers using different MCP SDK versions:

• Duplicate packages get installed
• Type mismatches when consumers reference MCP types (Tool, Prompt, Resource, ServerCapabilities) from their own code
• The agents package exposes MCP SDK types in its public API (e.g., MCPServersState, McpAgent.server)

Solution

• @modelcontextprotocol/sdk: required peer dep (>=1.0.0)

Unlike the AI SDK packages where some are optional, MCP is a required peer dependency because:

1. MCP functionality is core to the package (every Agent has this.mcp built-in)
2. Types like MCPServersState and McpAgent are fundamental exports
3. The McpAgent abstract class directly exposes McpServer | Server types

Breaking Changes

Consumers who don't already have @modelcontextprotocol/sdk installed will need to add it explicitly. However, anyone using MCP features is likely already interacting with MCP types.

Related to #42

🤖 Generated with Claude Code

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commit: 1c2efb4

[whoiskatrin]

@agcty don't merge it just yet, please

[threepointone]

because the mcp sdk does breaking changes in minors right now, I don't think we can actually guarantee this. not a great situation for us to be in unfortunately. we need to think through this.

tagging @mattzcarey for visibility

[threepointone]

blocking this while we figure out what to do here

[mattzcarey]

When MCP v2 lands we should be able to do this but for now this is gonna be super tough to support as their are breaking changes in every minor version atm