docs(omarchy): #78 Omarchy → Nomarchy migrant one-pager

Add docs/OMARCHY.md for users coming from Omarchy (VISION § F). Leads
with the one real difference — imperative dotfiles vs a declarative flake
built via the menu, with rollback through NixOS generations — then maps
the deltas: install (ISO/nomarchy-install or MIGRATION.md), a familiar
keybindings table, theming (SUPER+T / nomarchy-theme-sync), installing
software (home.packages / nix shell, no AUR), and update+rollback
(nomarchy-pull/-rebuild/-home, boot-menu generations, nomarchy-doctor).
Registered in docs/README.md; VISION § F marked shipped.

The Nomarchy side is grounded in the code: keybindings pulled from
keybinds.nix, and every cited command (7), the nsearch alias, and the
named theme slugs (gruvbox/rose-pine/nord) verified to exist. Omarchy-side
claims kept to known facts (Arch, dotfiles, pacman/AUR).

Verification: V0 (docs-only); commands/slugs/binds checked against the tree.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

agent/BACKLOG.md

@@ -150,20 +150,16 @@ _(Identity taste retunes + hand `btop.theme` for white/vantablack/lumon/
 
 ### Docs / narrative
 
-- **Omarchy migrant one-pager** (`VISION § F`) — no Omarchy→Nomarchy guide
-  exists (MIGRATION.md is NixOS→Nomarchy; RECOVERY is recovery). Omarchy is
-  the closest sibling and the likeliest source of new users. A short `docs/`
-  page mapping the deltas: keybindings, the theme system (`nomarchy-theme-sync`
-  vs Omarchy's), the install path (ISO vs Arch script), and what feels the
-  same (Hyprland/Waybar). Docs-only, low-risk, adoption-facing. Cost: small.
-  (Verified 2026-07-10: no "omarchy" mentions in docs beyond VISION's idea.)
+_(Omarchy migrant one-pager → shipped 2026-07-10 as **#78**:
+  `docs/OMARCHY.md` — config-model shift, install, bindings, theming,
+  packages, update/rollback; verified commands/slugs/binds.)_
 
 ### v1.0 pointer
 
-See **VISION**. Doctor hibernate section promoted → NEXT #77. Open
-PROPOSED: Omarchy migrant doc (`§F`); auto time-of-day theme pair (`§D`,
-big); NVIDIA wrappers deferred past v1; IR portal (b)/(c) hardware.
-Browser default = Chromium; power = PPD.
+See **VISION**. Shipped: doctor hibernate #77, Omarchy migrant doc #78.
+Open PROPOSED: auto time-of-day theme pair (`§D`, big); NVIDIA wrappers
+deferred past v1; IR portal (b)/(c) hardware. Browser default = Chromium;
+power = PPD.
 
 
 ## Decisions `[human]`