feat: add duplicate-safe workflow shadow dispatch

docs/workflows/WORKFLOW_DELIVERY_CHECKLIST.md

@@ -30,7 +30,7 @@
 - [x] Node outputs are persisted and reusable
 - [x] Graph runtime supports legacy fallback
 - [x] `legacy`, `graph`, and `shadow` modes exist
-- Progress: Workflow configs now normalize to an explicit execution mode, the editor exposes and persists `legacy`/`graph`/`shadow`, production order-line dispatch can opt into graph mode with hard fallback to legacy on graph failure, and shadow mode is stored safely while still deferring duplicate-safe parity execution to Phase 6.
+- Progress: Workflow configs now normalize to an explicit execution mode, the editor exposes and persists `legacy`/`graph`/`shadow`, production order-line dispatch can opt into graph mode with hard fallback to legacy on graph failure, and workflow runs now persist their execution mode for safer status tracking and rollout inspection.
 
 ### Phase 5
 
@@ -42,7 +42,7 @@
 
 ### Phase 6
 
-- [ ] Shadow mode parity checks run on real workflows
+- [x] Shadow mode parity execution dispatches real graph observer runs alongside authoritative legacy dispatch
 - [ ] Golden cases pass against legacy outputs
 - [ ] Rollout can be enabled per workflow or output type
 - [ ] Rollback to legacy is immediate

docs/workflows/WORKFLOW_IMPLEMENTATION_BACKLOG.md

@@ -92,7 +92,7 @@
 
 ### Tickets
 
-- `E6-T1` Add shadow mode parity execution.
+- `E6-T1` Add shadow mode parity execution. `completed`
 - `E6-T2` Build output comparison tooling.
 - `E6-T3` Define golden test cases.
 - `E6-T4` Roll out per workflow or output type.