[sebxt]

The generated parse_rfc3339 validator passes the string straight to datetime.strptime(..., "%Y-%m-%dT%H:%M:%S.%fZ"). %f only matches up to 6 digits, while the time crate's RFC 3339 serializer emits up to 9, so a value like 2024-05-01T12:34:56.123456789Z coming from a Rust service fails Pydantic validation.

This change truncates the fractional part to 6 digits before calling strptime. datetime only has microsecond precision, so nothing representable is lost. Strings without a fraction, or with 6 digits or fewer, are unchanged.

Changes:

• core/src/language/python.rs: trim the fraction in the emitted parse_rfc3339.
• Updated the test_serde_iso8601 and test_custom_serialize_deserialize_functions Python snapshots.

Testing:

• cargo test -p typeshare-core --test snapshot_tests passes (the two Python snapshots fail without the generator change).
• Loaded the generated test_serde_iso8601/output.py with pydantic 2 and validated {"time": "2024-05-01T12:34:56.123456789Z"}: before, ValidationError; after, 2024-05-01 12:34:56.123456. The 3 digit and no fraction cases behave as before.

Fixes #297