feat(deploy): HuggingFace Static Space for frontend (#34)

## Changes
- Add frontend/.env.production with backend API URL
- Update frontend/README.md with HF Spaces YAML metadata
- Add path-based CI filtering (dorny/paths-filter)
- Fix frontend-build conditional to handle skipped jobs
- Update spec 36 to document Vite 7 tsconfig pattern

## CI Optimization
- Backend jobs only run on src/, tests/, pyproject.toml changes
- Frontend jobs only run on frontend/** changes
- Push to main runs full CI (safety gate)

Co-authored-by: CodeRabbit <coderabbit@users.noreply.github.com>

.env.production

@@ -0,0 +1,3 @@
+# Production environment - HuggingFace Spaces deployment
+# Backend API running on Docker Space with T4 GPU
+VITE_API_URL=https://vibecodermcswaggins-stroke-deepisles-demo.hf.space

README.md

@@ -6,8 +6,7 @@ colorTo: purple
 sdk: static
 app_file: dist/index.html
 app_build_command: npm run build
-# CRITICAL: Vite 6 requires Node.js >= 20. HF Spaces defaults to Node 18.
-# Without this, the build will fail or produce warnings.
+# CRITICAL: Vite 7 requires Node.js >= 20. HF Spaces defaults to Node 18.
 nodejs_version: "20"
 pinned: false
 ---
@@ -61,5 +60,20 @@ npm run build        # Production build
 Set `VITE_API_URL` to point to your backend:
 
 ```bash
+# Local development (default)
 VITE_API_URL=http://localhost:7860 npm run dev
+
+# Production is configured in .env.production
+# Points to: https://vibecodermcswaggins-stroke-deepisles-demo.hf.space
+```
+
+## Deployment
+
+This frontend deploys as a **HuggingFace Static Space**. The backend API runs on a separate Docker Space with GPU.
+
+```bash
+# Build for production (uses .env.production)
+npm run build
+
+# The dist/ folder is deployed to HF Static Space
 ```