Plan-based caching with artifact playback in UI

RunStatus now stores:
- plan_id, plan_name for linking to execution plan
- step_results for per-step execution status
- all_outputs for all artifacts from all steps

Plan visualization:
- Shows human-readable step names from recipe structure
- Video/audio artifact preview on node click
- Outputs list with links to cached artifacts
- Stats reflect actual execution status (completed/cached/pending)

Execution:
- Step results include outputs list with cache_ids
- run_plan returns all outputs from all steps
- Support for completed_by_other status

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

tasks/execute.py

@@ -222,6 +222,32 @@ def execute_step(
         # Mark completed
         complete_task(step.cache_id, worker_id, str(cached_file.path))
 
+        # Build outputs list (for multi-output support)
+        outputs = []
+        if step.outputs:
+            # Use pre-defined outputs from step
+            for output_def in step.outputs:
+                outputs.append({
+                    "name": output_def.name,
+                    "cache_id": output_def.cache_id,
+                    "media_type": output_def.media_type,
+                    "index": output_def.index,
+                    "path": str(cached_file.path),
+                    "content_hash": cached_file.content_hash,
+                    "ipfs_cid": ipfs_cid,
+                })
+        else:
+            # Single output (backwards compat)
+            outputs.append({
+                "name": step.name or step.step_id,
+                "cache_id": step.cache_id,
+                "media_type": "video/mp4",
+                "index": 0,
+                "path": str(cached_file.path),
+                "content_hash": cached_file.content_hash,
+                "ipfs_cid": ipfs_cid,
+            })
+
         # Cleanup temp
         if output_dir.exists():
             import shutil
@@ -230,10 +256,12 @@ def execute_step(
         return {
             "status": "completed",
             "step_id": step.step_id,
+            "name": step.name,
             "cache_id": step.cache_id,
             "output_path": str(cached_file.path),
             "content_hash": cached_file.content_hash,
             "ipfs_cid": ipfs_cid,
+            "outputs": outputs,
         }
 
     except Exception as e: