feat(express): add jsonBodyLimit option to createMcpExpressApp

[corvid-agent]

Summary

• Adds a jsonBodyLimit option to CreateMcpExpressAppOptions to allow configuring the maximum request body size for the JSON body parser
• Accepts a number (bytes) or a string (e.g., '1mb', '500kb')
• Defaults to Express's built-in default of 100kb if not specified

Motivation

When MCP payloads exceed Express's default 100kb limit, the body parser rejects the request. This change allows users to configure the limit without needing to patch the package.

Closes #1354

Test plan

• Verify default behavior unchanged (no jsonBodyLimit = Express default 100kb)
• Verify custom limit works (e.g., jsonBodyLimit: '1mb')

🤖 Generated with Claude Code

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