fix(menu): Back audit — cheatsheet gets ↩ Back, exceptions documented (item 24)

Audited every rofi -dmenu call site in the generated nomarchy-menu +
nomarchy-vpn. The earlier "Back everywhere" pass held up: power,
power-profile, theme, clipboard, files, audio, display (both stages),
capture, tools, system and all four VPN lists already end in ↩ Back.

Fixed: the keybinds cheatsheet — Enter on any row silently closed it;
it now ends in ↩ Back returning to the root picker (its launch point),
and Enter elsewhere stays a deliberate no-op.

Documented (rofi.nix, at the convention comment + call sites): external
modi (rofi-calc, rofi-emoji, networkmanager_dmenu, rofi-pulse-select)
cannot take an injected row — Esc is their back path; free-text
prompts (web, ask) have no list to append to.

Verified: V0; V1 (built nomarchy-menu, bash -n OK; awk audit over the
generated script shows the only back-less lists are the root picker —
by design — and the free-text prompt). V3 spot-check queued.

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

agent/HARDWARE-QUEUE.md

@@ -49,6 +49,10 @@ QA machine), the **T14s** (webcam case).
       row, dimmed inactive workspaces / muted volume visible-but-dim),
       rofi inputbar/alternate rows show text. Spot-check one dark theme
       (e.g. tokyo-night) for no visual regression in the same spots.
+- [ ] **Back-audit spot-check** (item 24) — the keybinds cheatsheet
+      (SUPER+? / root menu › Keybindings) now ends in ↩ Back and
+      returns to the root picker; spot a couple of submenus (Display,
+      VPN › Tailscale) still Back correctly after the audit pass.
 - [ ] **Network menu has no blank rows** (item 22 fix, needs Wi-Fi) —
       after `home-update`, open Tools › Network: no empty separator
       rows between the ethernet/wifi/VPN sections (compact = True).