chore: upgrade jsonschema to 0.40 and schemars to 1.2

[yoskini]

• Update jsonschema dependency from 0.18 to 0.40
  • Update schemars dependency from 0.8 to 1.2
  • Adapt to new jsonschema API:
    • Replace JSONSchema::compile with validator_for
    • Replace validate().is_err() pattern with iter_errors
    • Update validation error handling to use iterator pattern
  • Adapt to new schemars API:
    • Change schema_name() return type to Cow<'static, str>
    • Remove deprecated is_referenceable() method
    • Rebuild Json

[Artifizer]

I see you introduce #/$defs/GtsInstanceId ... , that probably means the other ways of GTS ID reference are deprecated now, correct?

If yes, we'd need to:

1. Ensure all examples in all https://github.com/GlobalTypeSystem/ repos now switch to this new notation
2. Ensure spec documentation explains it @ https://github.com/GlobalTypeSystem/gts-spec
3. Ensure we have new pytests implemented in https://github.com/GlobalTypeSystem/gts-spec/tree/main/tests
4. Ensure we have proper notation being used @ https://github.com/hypernetix/hyperspot

[yoskini]

No, #/$defs/GtsInstanceId is not a new user-facing notation - it's an internal implementation detail that we immediately resolve.

This is purely a side effect of the schemars 0.8 → 1.2 upgrade. The schemars library changed how it generates schemas for custom types:

Before (schemars 0.8) - schemas were inlined:

{
  "properties": {
    "id": {
      "type": "string",
      "format": "gts-instance-id"
    }
  }
}

After (schemars 1.2) - schemas use $ref to $defs:

{
  "properties": {
    "id": {
      "$ref": "#/$defs/GtsInstanceId"
    }
  },
  "$defs": {
    "GtsInstanceId": {
      "type": "string",
      "format": "gts-instance-id"
    }
  }
}

In this fix the macro immediately resolves these back to inline schemas:

if ref_str == "#/$defs/GtsInstanceId" {
    *value = gts::GtsInstanceId::json_schema_value();
}

The #/$defs/GtsInstanceId pattern never appears in final schemas - it's resolved at compile time during macro expansion.