"One of" is incorrectly translated to merged object schema in JSON Schema and loses required field information

An array[NodeData], where NodeDate is defined as:

```
## NoteData (fixed-type)
+ One of
+ Properties
+ id: 1 (required, number) - Unique identifier
+ title: Grocery list (required) - Single line description
+ body: Buy milk - Full description of the note which supports Markdown.
+ Properties
+ id: 1 (required, number) - Unique identifier
+ title: Grocery list (required) - Single line description
+ body: Buy milk - Full description of the note which supports Markdown.
+ other: Other stuff (required)
```

produces, in the JSON schema:

```
{
"type": "array",
"items": {
"type": "object",
"properties": {
"id": {
"type": "number",
"description": "Unique identifier"
},
"title": {
"type": "string",
"description": "Single line description"
},
"body": {
"type": "string",
"description": "Full description of the note which supports Markdown."
},
"other": {
"type": "string"
}
},
"allOf": [
{
"not": {
"required": [
"id",
"title",
"body",
"id",
"title",
"body",
"other"
]
}
}
]
},
"$schema": "http://json-schema.org/draft-04/schema#"
}
```

Start by reproducing the JSON Schema conversion using the array[NodeData] example in the issue and compare the generated schema with the two intended object alternatives. Trace the conversion entry point for fixed-type "One of" blocks, then verify that the result preserves separate alternatives and each alternative's required fields.

Written by the indexing model from the issue text.