GH-116394
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Validate extension JSON: Error: Field 'classes/Animation/methods/get_length/return_value': meta changed value in new API, from "float" to "double".
Validate extension JSON: Error: Field 'classes/Animation/methods/set_length/arguments/0': meta changed value in new API, from "float" to "double".

Return type and parameter changed from real_t to double to match internals. No compatibility methods registered because GDExtension FFI already uses double.
