chore: polish repo for public release

Add MIT LICENSE, fix README clone URL and add CI/license badges,
flesh out setup.py metadata, add a GitHub Actions test workflow,
and remove dead code left over from earlier iterations.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

setup.py

@@ -3,6 +3,12 @@ from setuptools import setup, find_packages
 setup(
     name="x-space-downloader",
     version="0.1.0",
+    description="Download X (Twitter) Space recordings as MP4 replays or MP3 audio",
+    long_description=open("README.md", encoding="utf-8").read(),
+    long_description_content_type="text/markdown",
+    url="https://github.com/Dasemu/x-space-downloader",
+    author="Dario Sevilla",
+    license="MIT",
     packages=find_packages(),
     install_requires=[
         "yt-dlp>=2024.0.0",