fix: modify() preserve unknown top-level schema keys when using pick

[sandrina-p]

Bug

This bug happens in v1, but not in v0.

modify() used with pick silently drops any top-level schema key it doesn't explicitly know about (type, x-rmt-meta, additionalProperties, $schema, etc). Only properties, x-jsf-order, required, allOf, x-jsf-logic survived.

Repro:

const schema = {
  'type': 'object',
  'x-rmt-meta': { jsfOldVersion: true },
  'properties': {
    name: { type: 'string' },
    age: { type: 'number' },
  },
}

const { schema: result } = modify(schema, { pick: ['name'] })

result.type // undefined, should be 'object'
result['x-rmt-meta'] // undefined, should be { jsfOldVersion: true }

Fix

Added the missing default case so unrecognized top-level keys pass through unchanged, matching v0.

[nitin-remote]

Looks good, thank you!