docs(13-01): complete registry refactor and 18-backend expansion plan

- 13-01-SUMMARY.md: full execution summary with decisions, deviations, and task commits
- STATE.md: updated position to phase 13 plan 01 complete, added key decisions
- ROADMAP.md: 13-01 checked off, phase 13 progress 1/4
- REQUIREMENTS.md: REMOTE-01, REMOTE-02, REMOTE-06 marked complete (3/6 v1.3 requirements)

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

.planning/STATE.md

@@ -1,17 +1,17 @@
 ---
 gsd_state_version: 1.0
-milestone: v1.2
-milestone_name: UI Polish & Clarity
-status: completed
-stopped_at: Phase 13 context gathered
-last_updated: "2026-04-01T12:27:37.497Z"
-last_activity: 2026-04-01 — Phase 11 plan 02 complete (POLISH-03, POLISH-04 satisfied)
+milestone: v1.3
+milestone_name: Backend Expansion
+status: in-progress
+stopped_at: "Phase 13 plan 01 complete"
+last_updated: "2026-04-01T16:20:00Z"
+last_activity: 2026-04-01 — Phase 13 plan 01 complete (REMOTE-01, REMOTE-02, REMOTE-06 satisfied)
 progress:
-  total_phases: 6
-  completed_phases: 5
-  total_plans: 14
-  completed_plans: 14
-  percent: 100
+  total_phases: 7
+  completed_phases: 6
+  total_plans: 18
+  completed_plans: 15
+  percent: 83
 ---
 
 # Project State
@@ -25,12 +25,12 @@ See: .planning/PROJECT.md (updated 2026-03-31)
 
 ## Current Position
 
-Phase: 11 of 11 (Polish & Responsiveness) — Complete
-Plan: 11-02 (complete)
-Status: Phase 11 complete — all plans done (POLISH-01, POLISH-02, POLISH-03, POLISH-04 satisfied)
-Last activity: 2026-04-01 — Phase 11 plan 02 complete (POLISH-03, POLISH-04 satisfied)
+Phase: 13 of 13 (Add Remaining RClone Remotes) — In Progress
+Plan: 13-01 (complete)
+Status: Phase 13 plan 01 complete — registry refactor and 18-backend expansion done
+Last activity: 2026-04-01 — Phase 13 plan 01 complete (REMOTE-01, REMOTE-02, REMOTE-06 satisfied)
 
-Progress: [██████████] 100% (v1.2)
+Progress: [████████░░] 83% (v1.3)
 
 ## Accumulated Context
 
@@ -72,6 +72,10 @@ Recent decisions affecting current work:
 - [Phase 12-dark-mode-visibility-fixes]: bg-surface-container text-on-surface added to FieldRenderer select className — semantic tokens ensure correct rendering in both light and dark themes without dark: prefix
 - [Phase 12-dark-mode-visibility-fixes]: accent-[var(--r2b-warning)] arbitrary value used for ReviewStep security checkbox — accent-warning class not confirmed generated by Tailwind v4
 - [Phase 12-dark-mode-visibility-fixes]: Removed {' '} space-before-text pattern in DeploymentStep labels — replaced with flex gap-2 layout for consistent spacing
+- [Phase 13-01]: BackendType derived from keyof typeof BACKEND_REGISTRY — eliminates manual union maintenance at 18+ backends
+- [Phase 13-01]: Registry uses as const (not Record<BackendType,...> cast) — cast was circular when BackendType derived from registry
+- [Phase 13-01]: BACKEND_SCHEMAS auto-generated via Object.fromEntries over registry keys — no per-backend buildZodSchema call needed
+- [Phase 13-01]: Registry has 18 backends (http and seafile are separate entries; plan's "17" was a counting error)
 
 ### Roadmap Evolution
 
@@ -88,6 +92,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-04-01T12:27:37.494Z
-Stopped at: Phase 13 context gathered
-Resume file: .planning/phases/13-add-remaining-rclone-remotes/13-CONTEXT.md
+Last session: 2026-04-01T16:20:00Z
+Stopped at: Completed 13-01-PLAN.md
+Resume file: .planning/phases/13-add-remaining-rclone-remotes/13-01-SUMMARY.md