feat(mcp-server): add pure Koa MCP server implementation

[Scra3]

Summary

• Add a native Koa implementation of the MCP server that bypasses the Express-based handlers from @modelcontextprotocol/sdk
• This allows Forest Admin agent (Koa-based) to use MCP without Express bridging
• New exports: KoaMcpServer, KoaMcpServerOptions, createKoaMcpMiddleware

New files:

• koa-server.ts: Pure Koa MCP server with OAuth handlers
• koa-factory.ts: Factory function for creating Koa middleware

Key points:

• Reuses ForestOAuthProvider (framework-agnostic)
• Reimplements OAuth routes (authorize, token, metadata endpoints) in native Koa
• No Express dependency for Koa users
• Same OAuth flow and security as the Express version

Usage in Forest Agent:

import { createKoaMcpMiddleware } from '@forestadmin/mcp-server';

const mcpMiddleware = await createKoaMcpMiddleware({
  forestServerUrl: context.forestServerUrl,
  envSecret: context.envSecret,
  authSecret: context.authSecret,
  logger: context.logger,
}, { baseUrl: 'https://myapp.com' });

koaApp.use(mcpMiddleware);

Test plan

• All existing tests pass (216 tests)
• Build passes
• Manual testing with MCP client

🤖 Generated with Claude Code

[qltysh]

15 new issues

Tool	Category	Rule	Count
qlty	Structure	Function with high complexity (count = 19): useCallbackOnFastify	6
qlty	Structure	Function with many parameters (count = 4): exchangeAuthorizationCode	3
qlty	Structure	Deeply nested control flow (level = 4)	2
qlty	Duplication	Found 15 lines of similar code in 2 locations (mass = 69)	2
qlty	Structure	Function with many returns (count = 4): setupSuperagentMock	2