Parameter-level descriptions are ignored in Python SDK generation; only schema descriptions are used

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!

issue 中沒有指定來源檔案或測試。首先，根據提供的 OpenAPI 3.1 repro 產生 Python 用戶端，並檢查產生方法的引數文件。完成標準是使用 parameter.description 作為引數文件，同時保留 schema 描述，以提供型別或值格式的詳細資訊。