feat: workflow graph system — blocks 1-20 complete checkpoint

Full graph-based workflow execution engine with:
- WorkflowGraphRuntime with two-phase dispatch (collect → fire Celery tasks)
- Node registry with contract validation, socket types, execution kinds
- WorkflowRuntimeServices: preflight, context resolution, shadow-mode A/B
- WorkflowRouter: CRUD + dispatch/preflight/run-history API endpoints
- OutputTypeContracts: workflow binding, rollout-mode resolution
- Admin router: output-type workflow binding endpoints
- Frontend: complete workflow editor with drag-drop canvas, node inspector,
  module bundles, reference bundles, preflight panel, validation banner,
  authoring guidance, blueprint templates, shadow/rollout gate UI
- Tests: comprehensive coverage for all workflow modules
- Docs: NODE_CONTRACT_AUDIT and VALIDATION_ERROR_INVENTORY

All 20 blocks from NEXT_20_BLOCK_BATCH_PLAN completed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/workflows/workflowReferenceBundles.ts

@@ -14,7 +14,10 @@ import {
 } from './workflowGraphDraft'
 import type { WorkflowGraphFamily } from './workflowNodeLibrary'
 
-export type WorkflowReferenceBundleId = 'still_render_reference'
+export type WorkflowReferenceBundleId =
+  | 'still_render_reference'
+  | 'still_render_alpha_reference'
+  | 'still_render_blend_reference'
   | 'cad_intake_reference'
 
 export type WorkflowReferenceBundleDefinition = {
@@ -73,6 +76,43 @@ const WORKFLOW_REFERENCE_BUNDLE_REGISTRY: WorkflowReferenceBundleDefinition[] =
     ],
     stage: 'Reference Path',
   },
+  {
+    id: 'still_render_alpha_reference',
+    label: 'Still Render Alpha Reference',
+    shortLabel: 'Still Alpha',
+    description: 'Insert the canonical still-render path with transparent-alpha defaults so compositing-ready PNG outputs stay workflow-first.',
+    family: 'order_line',
+    stepIds: [
+      'order_line_setup',
+      'resolve_template',
+      'auto_populate_materials',
+      'glb_bbox',
+      'material_map_resolve',
+      'blender_still',
+      'output_save',
+      'notify',
+    ],
+    stage: 'Reference Path',
+  },
+  {
+    id: 'still_render_blend_reference',
+    label: 'Still Render + Blend Reference',
+    shortLabel: 'Still + Blend',
+    description: 'Insert the canonical still-render path plus explicit .blend export delivery nodes so still and blend output-types can bind to the same graph family cleanly.',
+    family: 'order_line',
+    stepIds: [
+      'order_line_setup',
+      'resolve_template',
+      'auto_populate_materials',
+      'glb_bbox',
+      'material_map_resolve',
+      'blender_still',
+      'output_save',
+      'notify',
+      'export_blend',
+    ],
+    stage: 'Reference Path',
+  },
 ]
 
 function buildNodeData(
@@ -102,6 +142,10 @@ function getReferenceTemplate(bundleId: WorkflowReferenceBundleId) {
       return toTemplate(buildWorkflowBlueprintConfig('cad_intake'))
     case 'still_render_reference':
       return toTemplate(buildWorkflowBlueprintConfig('still_graph_reference'))
+    case 'still_render_alpha_reference':
+      return toTemplate(buildWorkflowBlueprintConfig('still_graph_alpha_reference'))
+    case 'still_render_blend_reference':
+      return toTemplate(buildWorkflowBlueprintConfig('still_graph_blend_reference'))
     default:
       return null
   }