PR: Middleware Support for McpServer (Fixes #1238)

[ahammednibras8]

PR: Middleware Support for McpServer (Fixes #1238)

🚀 Summary

This PR implements a request-lifecycle middleware system for McpServer,
enabling cross-cutting concerns (logging, authentication, error handling) to be
applied consistently across all Tools, Resources, and Prompts.

It introduces a strictly ordered "Onion Model" execution pipeline ensuring:

1. Zero-Behavior Default: No overhead/changes if no middleware is
   registered.
2. Type Safety: Strictly typed context and zero any usage.
3. Safety: Lifecycle freezing (cannot add middleware after start) and
   double-invocation guards.

🛠️ Key Changes

• Core: Added private _executeRequest pipeline to McpServer.
• API: Added public use(middleware: McpMiddleware) method.
• Refactor: Wrapped setToolRequestHandlers, setResourceRequestHandlers,
  and setPromptRequestHandlers to utilize the pipeline.

🧪 Verification

• Automated Tests: Added packages/server/test/server/mcpServer.test.ts
  covering:
  • Execution Order (FIFO)
  • Short-circuiting
  • Error propagation (Upstream & Downstream)
  • Async timing & Double-next safety
• Manual Verification: Verified real-world "Logging + Auth" scenario in
  packages/server/examples/manual_verification.ts.
• Regressions: pnpm test (348 passing) and pnpm typecheck passed.

📝 Example Usage

server.use(async (context, next) => {
    console.log(`[${Date.now()}] ${context.request.method}`);
    try {
        await next(); // Execute next middleware/handler
    } catch (err) {
        console.error("Error intercepted:", err);
        throw err;
    }
});

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Latest commit: 7b88bd1

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[pkg-pr-new]

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npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1344

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1344

commit: 7b88bd1