[ylluminate]

A class with a field named _type made py2v fail on the whole file:

class Token:
    _type: str = "word"

Error parsing AST:
1:2661: Invalid json: Data: could not resolve sumtype `json2.Any` from "_type" field

The frontend wrote a class's field types and its field defaults as JSON objects keyed by the field name, and V's json2 reads a _type key in an object as a sum type tag when it decodes into json2.Any. Both are now written as lists of [name, value] pairs and read back that way, so a field name is never read as a key.

I ran into it on textual, in css/_style_properties.py.

Test plan

• tests/cases/class_field_named_type.py with its expected V. Master fails on it with the error above; with this change the emitted V builds and prints word, as Python does.
• v tests/run_tests.vsh: 179 passed, 0 failed (178 before, plus the new case), so every existing class case reads its fields and defaults the same through the new form.