We should be checking if the entrypoint file is in the current directory
before we validate that it's a valid python file. Otherwise, the error
message will be "invalid name for python file" when someone provides a
path to a valid python file.
<!-- CURSOR_SUMMARY -->
---
> [!NOTE]
> **Low Risk**
> Low risk: only adjusts input validation/error messaging for `arcade
configure` stdio entrypoints and bumps the package patch version.
>
> **Overview**
> Improves `arcade configure` stdio entrypoint validation by **rejecting
path-like values** (e.g., containing `/` or `\\`) before checking
filename format, producing a clearer error when users pass a path
instead of a file in the current directory.
>
> Bumps the project version from `1.13.0` to `1.13.1`.
>
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
4d02ee947740f839fd46d9faf62cfa766d5dae47. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->
82d6661dd9