Function patch_seq_variant_append 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn patch_seq_variant_append(
    stack: Stack,
) -> Stack

Append a value to a variant, returning a new variant

Stack effect: ( Variant Value – Variant’ )

Creates a new variant with the same tag as the input, but with the new value appended to its fields. The original variant is not modified (functional/immutable style).

Example: For arrays, [1, 2] 3 variant-append produces [1, 2, 3] Example: For objects, {} "key" variant-append "val" variant-append builds {"key": "val"}

Safety

Stack must have a Variant and a Value on top