fix: return protocol errors for invalid tool args

[he-yufeng]

Summary

• let invalid tool arguments surface as JSON-RPC InvalidParams errors
• keep actual tool execution failures wrapped as CallToolResult isError responses
• add an in-memory regression test for schema-invalid tools/call arguments

To verify

• pnpm --filter @modelcontextprotocol/server test -- test/server/mcp.compat.test.ts
• pnpm --filter @modelcontextprotocol/server typecheck
• pnpm --filter @modelcontextprotocol/server lint
• git diff --check

Fixes #2162

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Latest commit: 7641e96

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@modelcontextprotocol/client

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@modelcontextprotocol/codemod

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commit: 7641e96

[he-yufeng]

CI note: I checked the remaining red Node 20 job. The invalid-argument coverage added in this PR passes in that run; the failure is in test/server/cloudflareWorkers.test.ts with a Miniflare network connection lost error, which is outside the touched server validation path. I also tried to rerun the failed job, but GitHub requires repo admin rights for that.