No way to mark an array of `$ref` as a non-DB relation

[siggi-k]

A single $ref can already be declared as "not a foreign key" and then generates an abstract
getter the app implements itself:

document:
  allOf:
    - $ref: '#/components/schemas/Document'
    - x-db-type: false

abstract public function getDocument(): \yii\db\ActiveQuery;

For type: array there is no spec form that reaches this.

Wanted

One of these inputs should work (or both, whichever is cheaper):

# form 1
customFieldLeads:
  type: array
  readOnly: true
  x-db-type: false
  items:
    $ref: '#/components/schemas/Lead'

# form 2
customFieldLeads:
  allOf:
    - type: array
      readOnly: true
      items:
        $ref: '#/components/schemas/Lead'
    - x-db-type: false

The output must be identical to the plain form without the marker (property type, transformer
include, client relations() entry), with two differences: no DB column, and

-    public function getCustomFieldLeads()
-    {
-        return $this->hasMany(\common\models\Lead::class, ['order_id' => 'id'])->inverseOf('order');
-    }
+    abstract public function getCustomFieldLeads(): \yii\db\ActiveQuery;

Now

Form 1 throws:

InvalidDefinitionException: References not supported for virtual attributes
src/lib/AttributeResolver.php:306

Form 2 loses the whole inner schema. getAttr() reads the top level only, and the allOf loop in
PropertySchema::__construct() applies x-db-type: false only when the allOf holds a $ref.
The property degenerates to string and gets trim/string rules plus a real text column.

Root cause for both: initItemsReference() sets isNonDbReference only when the referenced
schema is non-DB (PropertySchema.php:217-219), never from the property's own x-db-type: false.