mcp: add tool call authentication state

[connor4312]

Summary

• add a resumable auth-required lifecycle state for MCP-contributed tool calls
• surface tool authentication challenges through session-level input-needed state
• add auth-required/auth-resolved actions and preserve tool-call state across pause/resume
• update reducers and generated clients for Go, Kotlin, Rust, and Swift
• document the authentication flow and add cross-language reducer fixtures

Testing

• npm run generate -- --allow-missing-formatter
• npm test
• TypeScript client: 63 tests passed
• Rust workspace: 75 tests passed
• Kotlin client: all tests passed
• Go client: all tests passed