feat(menu): Look & Feel category — theme, wallpaper, night light (item 19)

The gate was >=3 appearance entries and it's met: the root's Theme row
becomes "Look & Feel" (pango-escaped & — the root passes
-markup-rows; matched on *Look*), a new lookfeel submenu carries the
Theme grid (SUPER+T hint), Next wallpaper (SUPER+SHIFT+T hint via the
new generalized hintForAction, which menuHint is now sugar over), and
the Night light toggle moved out of System — which thins by one row.
The root stays at six entries; both direct binds still hit the leaves.

Verified: V0; V1 — rendered menu passes bash -n with the mode, escaped
label and relocated night-light row; visual — tokyo-night 1080p
capture renders "Look & Feel" correctly with hints intact. Submenu
flow queued for a session test (HARDWARE-QUEUE).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent/BACKLOG.md

@@ -222,11 +222,6 @@ the same `nomarchy-theme-sync` surface, + a first-boot guided
 (rollback menu, doctor, validation) are natural panels of it — design
 them as composable commands, not dead ends.
 
-### 19. Look & Feel menu category
-ROADMAP § Menu system, remaining: group Theme + night-light (+ wallpaper
-cycle, future appearance toggles) under a Look & Feel submenu once it
-earns ≥3 entries — keep the root at six.
-
 ## LATER
 
 - **Wallpapers artifact split** (ROADMAP § Faster switches — decided,