Describe the bug
When generating a Python client, parameter documentation is taken from the parameter schema’s description, while the parameter object’s top-level description is ignored or not preferred.

OpenAPI defines description on the Parameter Object (“A brief description of the parameter…”) and separately allows description on schemas via the Schema Object / JSON Schema annotation model. These fields describe different layers of the API, but the current Python generation appears to only use the schema-level description for parameter docs. 

OpenAPI Spec File

openapi: 3.1.0
info:
  title: Description precedence repro
  version: 1.0.0

paths:
  /tasks/export:
    get:
      operationId: export_tasks
      summary: Export tasks
      parameters:
        - in: query
          name: since
          required: false
          description: Only include tasks changed after this timestamp.
          schema:
            type: integer
            format: int64
            description: Unix timestamp in milliseconds.
      responses:
        "200":
          description: OK

Desktop (please complete the following information):

• OS: macOS Tahoe 26.3
• Python Version: 3.10
• openapi-python-client version: 0.28.2

Additional context
Expected behavior:

For simple parameters, generated method argument docs should prefer parameter.description, optionally appending schema.description as secondary value-format detail.

Example desired output:

def export_tasks(self, since: int | None = None) -> Response:
    """
    Args:
        since: Only include tasks changed after this timestamp.
               Unix timestamp in milliseconds.
    """

For reusable rich schemas, the split should be:

• method argument docs from parameter.description
• model/type docs from schema.description
• field docs from property description

This would preserve the distinction OpenAPI makes between operation-level parameter semantics and reusable type semantics. This seems to be true for response bodies too.

Happy to work on this myself!