feat: link effect to specific git commit for provenance

- Capture effects repo commit hash at render time
- Store effects_commit in run record
- Effect URLs now link to exact commit, not main branch
- Include commit in raw JSON provenance

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

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

tasks.py

@@ -7,6 +7,7 @@ Distributed rendering tasks for the Art DAG system.
 import hashlib
 import json
 import os
+import subprocess
 import sys
 from datetime import datetime, timezone
 from pathlib import Path
@@ -16,6 +17,24 @@ from celery_app import app
 
 # Add effects to path (use env var in Docker, fallback to home dir locally)
 EFFECTS_PATH = Path(os.environ.get("EFFECTS_PATH", str(Path.home() / "artdag-effects")))
+
+
+def get_effects_commit() -> str:
+    """Get current git commit hash of effects repo."""
+    try:
+        result = subprocess.run(
+            ["git", "rev-parse", "HEAD"],
+            cwd=EFFECTS_PATH,
+            capture_output=True,
+            text=True
+        )
+        if result.returncode == 0:
+            return result.stdout.strip()
+    except Exception:
+        pass
+    return "unknown"
+
+
 sys.path.insert(0, str(EFFECTS_PATH / "dog"))
 
 
@@ -106,6 +125,9 @@ def render_effect(self, input_hash: str, effect_name: str, output_name: str) ->
     if output_hash != expected_hash:
         raise ValueError(f"Output hash mismatch: expected {expected_hash}, got {output_hash}")
 
+    # Get effects repo commit
+    effects_commit = get_effects_commit()
+
     # Build provenance
     provenance = {
         "task_id": self.request.id,
@@ -120,7 +142,12 @@ def render_effect(self, input_hash: str, effect_name: str, output_name: str) ->
             {"content_hash": input_hash}
         ],
         "effects": [
-            {"name": f"effect:{effect_name}", "content_hash": REGISTRY[f"effect:{effect_name}"]["hash"]}
+            {
+                "name": f"effect:{effect_name}",
+                "content_hash": REGISTRY[f"effect:{effect_name}"]["hash"],
+                "repo_commit": effects_commit,
+                "repo_url": f"https://git.rose-ash.com/art-dag/effects/src/commit/{effects_commit}/{effect_name}"
+            }
         ],
         "infrastructure": {
             "software": {"name": "infra:artdag", "content_hash": REGISTRY["infra:artdag"]["hash"]},