fix: widen requestedSchema type to accept standard JSON Schema output

[kai-agent-free]

Summary

Fixes #1362 — Zod's .toJSONSchema() output type is incompatible with elicitInput()'s requestedSchema parameter.

Problem

JSON Schema generators like Zod v4's .toJSONSchema() produce standard fields ($schema, additionalProperties) that the narrow requestedSchema type rejects at the TypeScript level. The runtime behavior is correct — this is purely a type-def issue.

Changes

packages/core/src/types/spec.types.ts (interface):

• Added additionalProperties?: boolean | { [key: string]: unknown } as explicit optional field
• Added [key: string]: unknown index signature to allow any additional JSON Schema fields

packages/core/src/types/types.ts (Zod schema):

• Added additionalProperties as explicit optional field in the Zod object schema
• Added .passthrough() so extra JSON Schema fields survive runtime validation

Testing

• All existing tests pass (385/385, only pre-existing Cloudflare Workers port conflict skipped)
• TypeScript typecheck passes
• Build succeeds

Before/After

// Before: TS error
const result = await server.elicitInput({
  mode: 'form',
  message: 'Enter data',
  requestedSchema: z.object({ name: z.string() }).toJSONSchema()
  // ❌ Type error: $schema, additionalProperties not allowed
});

// After: works
const result = await server.elicitInput({
  mode: 'form', 
  message: 'Enter data',
  requestedSchema: z.object({ name: z.string() }).toJSONSchema()
  // ✅ Extra JSON Schema fields accepted
});

[changeset-bot]

🦋 Changeset detected

Latest commit: 6c078e7

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commit: 6c078e7

[felixweinberger]

Thanks for the contribution! Closing in favor of #1768.