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/BACKLOG.md

@@ -25,16 +25,6 @@ next, in what order*.
 *Items 21–27: real-hardware QA findings from the Latitude 5410
 (Bernardo, 2026-07-04) — bugs found on metal outrank the queue.*
 
-### 24. "Back" audit — every list menu ends in ↩ Back
-Reported: some submenu items/tools still lack a Back option. The "Back
-everywhere" pass covered the hand-rolled dmenu lists at the time; audit
-what's been added since (VPN, Display, power-profile, printers…) and
-the external/plugin modules (networkmanager_dmenu, rofi-pulse-select,
-rofi-calc/emoji modi) — hand-rolled lists get the shared `back` helper;
-external modi that can't take an injected row get documented as such
-(and Esc always works). **Verify:** V1 + a grep-the-generated-script
-audit listing which menus have/lack Back; V3 spot-check.
-
 ### 6. Full docs review & restructure
 ROADMAP § Full docs review. The roadmap/backlog split is done (this
 file); remaining: reconcile every README option table against the live