Fix artifact dict key mismatch (hash -> cid)

Template runs/detail.html expects artifact.cid but code provided
artifact.hash, causing UndefinedError when viewing run details.

- Change run_service.get_run_artifacts to return 'cid' key
- Change runs.py router inline artifact creation to use 'cid' key
- Add regression tests for artifact data structure

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

app/routers/runs.py

@@ -258,7 +258,7 @@ async def get_run(
             except Exception:
                 pass
             artifacts.append({
-                "hash": output_cid,
+                "cid": output_cid,
                 "step_name": "Output",
                 "media_type": media_type or "application/octet-stream",
             })

app/services/run_service.py

@@ -547,7 +547,7 @@ class RunService:
                 path = self.cache.get_by_cid(cid)
                 if path and path.exists():
                     return {
-                        "hash": cid,
+                        "cid": cid,
                         "size_bytes": path.stat().st_size,
                         "media_type": detect_media_type(path),
                         "role": role,

tests/test_run_artifacts.py

@@ -0,0 +1,57 @@
+"""
+Tests for run artifacts data structure.
+
+Bug found 2026-01-12: runs/detail.html template expects artifact.cid
+but the route provides artifact.hash, causing UndefinedError.
+"""
+
+import pytest
+from pathlib import Path
+
+
+class TestArtifactDataStructure:
+    """Tests for artifact dict keys matching template expectations."""
+
+    def test_template_expects_cid_key(self) -> None:
+        """Template uses artifact.cid - verify this expectation."""
+        template_path = Path('/home/giles/art/art-celery/app/templates/runs/detail.html')
+        content = template_path.read_text()
+
+        # Template uses artifact.cid in multiple places
+        assert 'artifact.cid' in content, "Template should reference artifact.cid"
+
+    def test_run_service_artifacts_have_cid_key(self) -> None:
+        """
+        Regression test: get_run_artifacts must return dicts with 'cid' key.
+
+        Bug: Service returned artifacts with 'hash' key but template expected 'cid'.
+        Fix: Changed service to use 'cid' key for consistency.
+        """
+        # Read the run_service.py file and check it uses 'cid' not 'hash'
+        service_path = Path('/home/giles/art/art-celery/app/services/run_service.py')
+        content = service_path.read_text()
+
+        # Find the get_artifact_info function and check it returns 'cid'
+        # The function should have: "cid": cid, not "hash": cid
+        assert '"cid": cid' in content or "'cid': cid" in content, \
+            "get_run_artifacts should return artifacts with 'cid' key, not 'hash'"
+
+    def test_router_artifacts_have_cid_key(self) -> None:
+        """
+        Regression test: inline artifact creation in router must use 'cid' key.
+
+        Bug: Router created artifacts with 'hash' key but template expected 'cid'.
+        """
+        router_path = Path('/home/giles/art/art-celery/app/routers/runs.py')
+        content = router_path.read_text()
+
+        # Check that artifacts.append uses 'cid' key
+        # Should have: "cid": output_cid, not "hash": output_cid
+        # Count occurrences of the patterns
+        hash_pattern_count = content.count('"hash": output_cid')
+        cid_pattern_count = content.count('"cid": output_cid')
+
+        assert cid_pattern_count > 0, \
+            "Router should create artifacts with 'cid' key"
+        assert hash_pattern_count == 0, \
+            "Router should not use 'hash' key for artifacts (template expects 'cid')"