docs(08.1): create phase plans for contraction hierarchies routing backend v3

.planning/ROADMAP.md

@@ -296,13 +296,15 @@ Notes:
 
 ### Phase 08.1: Contraction Hierarchies (Routing Backend v3) — the lever that closes SC-1: build-time node ordering + contraction + shortcut edges, simple uphill bidirectional query, optimality by construction (INSERTED)
 
-**Goal:** [Urgent work - to be planned]
-**Requirements**: TBD
+**Goal:** Build-time node ordering + contraction + shortcut edges over the KL road graph, a simple uphill bidirectional query replacing the ALT-steered bidirectional A* as THE one search path, and optimality by construction — so cross-metro routes finally route inside the free-plan CPU budget and the c3 degradation class retires with measured evidence (or the record shrinks honestly if the measurement says otherwise).
+**Requirements**: ROADMAP-08.1-GOAL, D-01..D-13 (phase-scoped decisions; no v1 REQ ids added)
 **Depends on:** Phase 8
-**Plans:** 5/5 plans complete
+**Plans:** 3 plans
 
 Plans:
-- [ ] TBD (run /gsd-plan-phase 08.1 to break down)
+- [ ] 08.1-01-PLAN.md — Pure CH construction core + ARG3 codec + uphill bidirectional CH query as the sole search path; ALT deleted; ARG3 fixtures and bot graph builders rebuilt (D-04/D-05/D-07/D-10/D-11/D-12)
+- [ ] 08.1-02-PLAN.md — CH production build stage + measured ARG3 build + unchanged D-13 optimality/oracle gates + local CPU verdict and conditional D-03 drift-guard re-anchor (D-01/D-02/D-03/D-08/D-09/D-13)
+- [ ] 08.1-03-PLAN.md — Public ARG3 fork contract + measured c3 retire-or-shrink record + direction-split experiment closed as superseded (D-01/D-03/D-06/D-08/D-09/D-10/D-13)
 
 ### Phase 9: Routing Extras (Toll / Speed / Share / Voice)
 **Goal**: The REQUIREMENTS extras go live on the engine-A stack.