`.register_tool(model=MyParams)` errors unexpectedly when `MyParams` contains `Field(alias=...)`

[cpsievert]

For example

import chatlas as ctl
from pydantic import BaseModel, Field

chat = ctl.ChatAuto(provider="openai")

class MyParams(BaseModel):
    n: int = Field(..., description="Number of items to list", alias="_n")

def list_items(_n: int):
    return [f"Item {i + 1}" for i in range(_n)]

chat.register_tool(list_items, model=MyParams)

ValueError: `model` fields must match tool function parameters exactly. Fields found in one but not the other: {'n', '_n'}

Note that Field(alias=...) is the only way to create a BaseModel where the field starts with _*. This is, in turn, a problem for shinychat's tool calling UI where _intent is a special parameter.