Support minItems and maxItems in config array schemas

Context

VS Code has a session-mutable configuration property that is represented as an array with a zero-or-one-item contract:

https://github.com/microsoft/vscode/pull/332593

The current Agent Host Protocol ConfigPropertySchema can describe type: "array" and its items, but cannot express array cardinality.

Ask

Please add JSON Schema-compatible array cardinality fields:

interface ConfigPropertySchema {
    minItems?: number;
    maxItems?: number;
}

Servers and generated clients should carry these fields through schema serialization and validate them consistently.

Consumer requirement

VS Code needs to advertise maxItems: 1 for a session config array so clients cannot persist a value that passes the protocol schema but is later rejected by the provider's narrower runtime validation.

Start by locating the TypeScript ConfigPropertySchema definition and the existing schema serialization, generated client, and validation tests. Add coverage for minItems and maxItems, including the zero-or-one-item case, and verify that servers and clients preserve and enforce both fields consistently.