Add identity-then-dog recipe

Chains identity effect followed by dog effect on cat input.
Demonstrates effect chaining: SOURCE → EFFECT → EFFECT → output

Since identity(cat) = cat, the result is dog(cat) = dog video.

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

render_dog_cat.py

@@ -0,0 +1,101 @@
+#!/usr/bin/env python3
+"""
+Render dog(cat) - apply dog effect to cat image.
+
+Records full provenance: inputs, effects, software, hardware, owner.
+"""
+
+import hashlib
+import json
+import shutil
+import sys
+from datetime import datetime, timezone
+from pathlib import Path
+
+# Add effect to path
+sys.path.insert(0, str(Path(__file__).parent.parent / "artdag-effects" / "dog"))
+
+from effect import effect_dog, DOG_HASH
+
+
+def file_hash(path: Path) -> str:
+    """Compute SHA3-256 hash of a file."""
+    hasher = hashlib.sha3_256()
+    actual_path = path.resolve() if path.is_symlink() else path
+    with open(actual_path, "rb") as f:
+        for chunk in iter(lambda: f.read(65536), b""):
+            hasher.update(chunk)
+    return hasher.hexdigest()
+
+
+def main():
+    # Registry hashes
+    CAT_HASH = "33268b6e167deaf018cc538de12dbe562612b33e89a749391cef855b320a269b"
+    DOG_EFFECT_HASH = "d048fe313433eb4e38f0e24194ffae91b896ca3e6eed3e50b2cc37b7be495555"
+    ARTDAG_HASH = "96a5972de216aee12ec794dcad5f9360da2e676171eabf24a46dfe1ee5fee4b0"
+    WORKSTATION_HASH = "964bf6e69dc4e2493f42375013caffe26404ec3cf8eb5d9bc170cd42a361523b"
+
+    # Input (cat)
+    cat_path = Path.home() / "artdag-art" / "cat.jpg"
+    output_dir = Path.home() / "artdag-art"
+    output_path = output_dir / "dog-from-cat.mkv"
+
+    print("=== Rendering dog(cat) ===\n")
+
+    # Verify input
+    input_hash = file_hash(cat_path)
+    print(f"Input: {cat_path}")
+    print(f"Input hash: {input_hash}")
+    assert input_hash == CAT_HASH, f"Input hash mismatch! Expected {CAT_HASH}"
+
+    # Apply dog effect
+    print(f"\nApplying dog effect...")
+    result = effect_dog(cat_path, output_path, {})
+
+    # Verify output
+    output_hash = file_hash(result)
+    print(f"\nOutput: {result}")
+    print(f"Output hash: {output_hash}")
+    assert output_hash == DOG_HASH, f"Output hash mismatch! Expected {DOG_HASH}"
+
+    print(f"\n✓ dog(cat) = dog.mkv")
+    print(f"  Cat went in, dog came out!")
+
+    # Record provenance
+    provenance = {
+        "minted_at": datetime.now(timezone.utc).isoformat(),
+        "minted_by": "@giles@artdag.rose-ash.com",
+        "output": {
+            "name": "dog-from-cat",
+            "content_hash": output_hash,
+            "local_path": str(result),
+            "url": None,  # To be filled after push
+        },
+        "inputs": [
+            {"name": "cat", "content_hash": CAT_HASH}
+        ],
+        "recipe": {
+            "name": "dog-cat",
+            "description": "Apply dog effect to cat"
+        },
+        "effects": [
+            {"name": "effect:dog", "content_hash": DOG_EFFECT_HASH}
+        ],
+        "infrastructure": {
+            "software": {"name": "infra:artdag", "content_hash": ARTDAG_HASH},
+            "hardware": {"name": "infra:giles-hp", "content_hash": WORKSTATION_HASH}
+        }
+    }
+
+    # Save provenance
+    provenance_path = result.with_suffix(".provenance.json")
+    with open(provenance_path, "w") as f:
+        json.dump(provenance, f, indent=2)
+
+    print(f"\nProvenance saved: {provenance_path}")
+
+    return provenance
+
+
+if __name__ == "__main__":
+    main()