fix(core): allow additional JSON Schema properties in elicitInput requestedSchema

[corvid-agent]

Summary

• Adds .catchall(z.unknown()) to the requestedSchema object type in ElicitRequestFormParamsSchema, matching the existing pattern used by inputSchema and outputSchema for tool definitions
• This allows Zod v4's .toJSONSchema() output (which includes extra properties like $schema and additionalProperties) to be passed directly to elicitInput() without type errors

Problem

When using Zod v4's .toJSONSchema() to generate a schema for elicitInput, the resulting object includes standard JSON Schema properties like $schema and additionalProperties that are not present in the requestedSchema TypeScript type. This works at runtime but fails type-checking, forcing users to use type casts.

// This fails type-checking today:
const result = await server.elicitInput({
  mode: 'form',
  message: 'Enter info',
  requestedSchema: z.object({ name: z.string() }).toJSONSchema()
  //                ^^^^^^^^ Type error: $schema, additionalProperties not assignable
});

Fix

The fix follows the same pattern already established in this codebase for inputSchema and outputSchema (lines 1391-1409 of types.ts), which use .catchall(z.unknown()) to accept additional JSON Schema properties beyond the required type, properties, and required fields.

The spec type in spec.types.ts already includes $schema?: string in its requestedSchema definition (line 2155), confirming that additional properties are expected.

Fixes #1362

Test plan

• Existing elicitation tests continue to pass (no behavioral change -- .catchall(z.unknown()) only widens the accepted type)
• Spec type compatibility test (spec.types.test.ts) continues to pass (.catchall(z.unknown()) adds an index signature which is structurally compatible)
• Verify that z.object({ name: z.string() }).toJSONSchema() is now accepted by elicitInput without type errors

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 5725802

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@modelcontextprotocol/core	Patch

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