feat: distributed rendering with Celery

- celery_app.py: Celery configuration with Redis broker
- tasks.py: render_effect task with full provenance tracking
- render.py: CLI for submitting render jobs
- Successfully renders cat → dog with provenance chain

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

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+# Art Celery
+
+Distributed rendering for the Art DAG system using Celery.
+
+## Dependencies
+
+- **artdag** (GitHub): Core DAG execution engine
+- **artdag-effects** (rose-ash): Effect implementations
+- **Redis**: Message broker and result backend
+
+## Setup
+
+```bash
+# Install Redis
+sudo apt install redis-server
+
+# Install Python dependencies
+pip install -r requirements.txt
+
+# Start a worker
+celery -A celery_app worker --loglevel=info
+```
+
+## Usage
+
+```bash
+# Render cat through dog effect
+python render.py dog cat --sync
+
+# Render cat through identity effect
+python render.py identity cat --sync
+
+# Submit async (don't wait)
+python render.py dog cat
+```
+
+## Architecture
+
+```
+render.py (CLI)
+    │
+    ▼
+celery_app.py (Celery broker)
+    │
+    ▼
+tasks.py (render_effect task)
+    │
+    ├── artdag (GitHub) - DAG execution
+    └── artdag-effects (rose-ash) - Effect implementations
+           │
+           ▼
+       Provenance JSON + Output file
+```
+
+## Provenance
+
+Every render produces a provenance record:
+
+```json
+{
+  "task_id": "celery-task-uuid",
+  "rendered_at": "2026-01-07T...",
+  "rendered_by": "@giles@artdag.rose-ash.com",
+  "output": {"name": "...", "content_hash": "..."},
+  "inputs": [...],
+  "effects": [...],
+  "infrastructure": {
+    "software": {"name": "infra:artdag", "content_hash": "..."},
+    "hardware": {"name": "infra:giles-hp", "content_hash": "..."}
+  }
+}
+```