docs(11-01): complete sort_order + reorder backend plan

- Create 11-01-SUMMARY.md with full execution record
- Update STATE.md: progress 89%, decisions, metrics, session
- Update ROADMAP.md: phase 11 marked in-progress (1/2 plans)
- Mark requirements RANK-01, RANK-04, RANK-05 complete

.planning/ROADMAP.md

@@ -69,7 +69,7 @@ Plans:
   2. The reordered sequence is still intact after navigating away and returning
   3. The top three candidates display gold, silver, and bronze rank badges respectively
   4. Drag handles and rank badges are absent on a resolved thread; candidates render in static order
-**Plans:** 2 plans
+**Plans:** 1/2 plans executed
 Plans:
 - [ ] 11-01-PLAN.md — Schema migration, reorder service/route, sort_order persistence + tests
 - [ ] 11-02-PLAN.md — Drag-to-reorder UI, list/grid toggle, rank badges, resolved-thread guard
@@ -110,6 +110,6 @@ Plans:
 | 8. Search, Filter, and Candidate Status | v1.2 | 2/2 | Complete | 2026-03-16 |
 | 9. Weight Classification and Visualization | v1.2 | 2/2 | Complete | 2026-03-16 |
 | 10. Schema Foundation + Pros/Cons Fields | v1.3 | 1/1 | Complete | 2026-03-16 |
-| 11. Candidate Ranking | v1.3 | 0/2 | Not started | - |
+| 11. Candidate Ranking | 1/2 | In Progress|  | - |
 | 12. Comparison View | v1.3 | 0/TBD | Not started | - |
 | 13. Setup Impact Preview | v1.3 | 0/TBD | Not started | - |