fix: add short_description to Space YAML front matter

Replaces the default Gradio placeholder text on the HF activity feed
and Space card.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

README.md

@@ -9,6 +9,7 @@ app_file: app.py
 hf_oauth: true
 pinned: false
 license: mit
+short_description: Rank AI coding operators by architecture, not budget. Υ = (Cache·Output)/Input²
 models:
   - openbmb/MiniCPM4-0.5B
 tags: