docs: update README with repo URL, add setup guide and .gitignore

- Update README installation to use uv tool install with self-hosted repo URL
- Add docs/SETUP.md for AI agent consumption
- Add .gitignore for __pycache__, build artifacts, venv, IDE files
- Remove obsolete superpowers planning docs

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docs/SETUP.md

@@ -0,0 +1,23 @@
+# jianda-proxy Setup Guide
+
+## Install
+
+```bash
+uv tool install git+ssh://git@git.zz.com:2222/Developer/jianda-proxy.git
+```
+
+## Git Config
+
+After installation, run once to route LFS requests through the proxy:
+
+```bash
+git config --global http.http://git.zz.com:3000/.proxy http://127.0.0.1:13000
+```
+
+## Start Proxy
+
+```bash
+jianda-proxy start
+```
+
+After that, `git clone` / `git pull` / `git push` over SSH will automatically use the proxy for LFS downloads. No extra steps needed.