conductor(plan): mark Task 1.6 + 1.7 + 1.8 as complete (done by 2026-06-11 refresh)

conductor/tracks/data_oriented_error_handling_20260606/plan.md

@@ -560,7 +560,7 @@ to the remaining `src/` files (see `conductor/tracks/data_oriented_error_handlin
 §12.2 for the prioritized list).
 ```
 
-- [ ] **Step 3: Commit**
+- [x] **Step 3: Commit** (DONE 2026-06-11 by commit 85cf3fbd; section exists at line 50, more complete than the plan's spec with `Optional[T]` ban + deprecation sub-sections)
 
 ```bash
 git add conductor/product-guidelines.md
@@ -585,7 +585,7 @@ Add a new bullet in the Code Style section:
 - For error handling, see [Data-Oriented Error Handling](./code_styleguides/error_handling.md).
 ```
 
-- [ ] **Step 3: Commit**
+- [x] **Step 3: Commit** (DONE 2026-06-11 by commit 85cf3fbd; Code Style section line 12 already has the link with full convention summary)
 
 ```bash
 git add conductor/workflow.md