feat: add certificate trust configuration for MCP servers

[daniel-lxs]

Summary

This PR addresses Issue #8355 by adding certificate trust configuration support for MCP servers using HTTPS connections (SSE and StreamableHTTP transports).

Problem

MCP servers using self-signed or internal CA-signed certificates cannot be used because there's no way to specify trust information for these certificates. This prevents users from connecting to MCP servers in development environments or corporate networks with internal certificate authorities.

Solution

Added a certificateTrust configuration option for SSE and StreamableHTTP server types with three settings:

• allowSelfSigned: Allow self-signed certificates (for development)
• caCertPath: Path to custom CA certificate file (for internal CAs)
• rejectUnauthorized: Control certificate validation (defaults to true for security)

Changes

• ✅ Added CertificateTrustSchema to validate certificate trust configuration
• ✅ Implemented HTTPS agent configuration for SSE transport using custom fetch
• ✅ Implemented HTTPS agent configuration for StreamableHTTP transport
• ✅ Added comprehensive test coverage for all configuration scenarios
• ✅ Created detailed documentation with examples and security considerations

Testing

• All existing tests pass
• Added 6 new test cases covering certificate trust configuration
• TypeScript type checking passes
• Linting passes

Security Considerations

• Defaults to secure settings (rejectUnauthorized: true)
• Documentation includes clear warnings about development-only settings
• Proper error handling for certificate file loading

Documentation

Added comprehensive documentation in docs/mcp-certificate-trust.md including:

• Configuration examples for all scenarios
• Security best practices
• Certificate format conversion instructions
• Troubleshooting guide

[daniel-lxs]

Node 18+ global fetch (undici) ignores RequestInit.agent, so these certificateTrust settings won’t take effect for StreamableHTTP. Use undici’s dispatcher instead. Suggest: create an undici Agent with TLS options (e.g., new Agent({ connect: { tls: { rejectUnauthorized: false, ca: caCert } } })) and set (requestInit as any).dispatcher = agent. This also applies to the SSE custom fetch.

[daniel-lxs]

SSE path: the custom fetch adds { agent } to RequestInit, but Node’s global fetch (undici) ignores agent. Use undici’s dispatcher instead. Create an undici Agent/Pool with TLS options (e.g., new Agent({ connect: { tls: { rejectUnauthorized: false, ca: caCert } } })) and call fetch(url, { ...init, headers, dispatcher }). Consider caching the dispatcher per server to avoid recreating it on reconnect.

[daniel-lxs]

Limitation note: In Node 18+ the global fetch is powered by undici and ignores RequestInit.agent. For certificate overrides (custom CA, self-signed, disabling verification) you must use undici’s dispatcher (e.g., an undici Agent/Pool with TLS options) and pass it via fetch(..., { dispatcher }). Consider adding this to the Limitations with a short example so users don’t expect agent to work in Node.

[roo-code-dan]

This test commit message should be removed before merging the PR.