Python SDK models are not rebuilt on normal import

[enguerran-leclerc]

Repro

From a fresh install of the SDK, run:

from agent_platform import Client, SessionRequest
from agent_platform.api.agents import list_agents
from agent_platform.models.user_message_event import UserMessageEvent

client = Client(api_key=\"hk-...\")
list_agents.sync(client=client, size=5)
SessionRequest(
    agent=\"h/web\",
    messages=[UserMessageEvent(message=\"Open https://example.com\")],
)

Actual

Pydantic raises errors such as:

PydanticUserError: `Agent` is not fully defined; you should define `Browser`, then call `Agent.model_rebuild()`.
PydanticUserError: `SessionRequest` is not fully defined; you should define `Agent`, then call `SessionRequest.model_rebuild()`.

The integration test fixtures currently rebuild all generated models as a workaround, but normal SDK users do not get that setup.

Expected

Importing agent_platform should leave generated Pydantic models ready for normal instantiation and API response parsing.