Fix: remove gradio from requirements.txt, bump sdk_version to 6.17.3

HF Spaces pins gradio to sdk_version in README frontmatter.
Having gradio also in requirements.txt caused an irresolvable conflict.
Rule added to CLAUDE.md: never put gradio in requirements.txt.

CLAUDE.md

@@ -11,6 +11,15 @@ Stack: Python · Gradio · diffusers · HuggingFace Spaces (ZeroGPU).
 2. SYNTAX → ~/miniforge3/bin/python3 -c "import ast; [ast.parse(open(f).read()) for f in ['app.py','image_generator.py','math_engine.py']]"
 3. IMPORT → ~/miniforge3/bin/python3 -c "import app" 2>&1   # catches version conflicts & bad imports
              must produce NO errors (warnings OK)
+   SDK CHK → verify README.md sdk_version matches local gradio (HF Spaces pins gradio to sdk_version):
+             python3 -c "
+             import re, subprocess
+             sdk = re.search(r'sdk_version: \"(.+?)\"', open('README.md').read()).group(1)
+             local = subprocess.check_output(['pip','show','gradio']).decode()
+             ver = re.search(r'Version: (.+)', local).group(1)
+             assert sdk == ver, f'MISMATCH: README sdk_version={sdk} but local gradio={ver}'
+             print(f'✅ sdk_version {sdk} matches local gradio')
+             " 2>&1
 4. RUN    → kill previous instance, start fresh:
              pkill -f "python3 app.py"; ~/miniforge3/bin/python3 app.py > /tmp/numzoo.log 2>&1 &
              sleep 10 && cat /tmp/numzoo.log   # must show no errors
@@ -22,7 +31,10 @@ Stack: Python · Gradio · diffusers · HuggingFace Spaces (ZeroGPU).
              git add -A && git commit -m "..." && git push origin main
 ```
 
-**Version pinning rule:** always pin `gradio>=6.0.0` — older Gradio uses `HfFolder` which was removed from `huggingface_hub>=1.0`. Step 3 (import check) will catch this class of error locally.
+**Version pinning rules:**
+- **Never put `gradio` in `requirements.txt`** — HF Spaces installs it separately using `sdk_version` from README.md frontmatter. Conflicting versions cause build failure.
+- **Always keep `sdk_version` in README.md in sync with local gradio** — run the SDK check above before every push.
+- To upgrade gradio: update `sdk_version` in README.md, reinstall locally (`pip install gradio==x.y.z`), re-run full loop.
 
 **Never push broken code.** If Puppeteer tests fail, do not proceed to push.
 

README.md

@@ -4,7 +4,7 @@ emoji: 🦁
 colorFrom: purple
 colorTo: pink
 sdk: gradio
-sdk_version: "4.40.0"
+sdk_version: "6.17.3"
 app_file: app.py
 pinned: false
 license: apache-2.0

requirements.txt

@@ -1,4 +1,3 @@
-gradio>=6.0.0
 audioop-lts
 diffusers>=0.30.0
 transformers>=4.44.0