feat(rofi): battery charge-limit toggle in the System menu

Add a `batterylimit` nomarchy-menu subcommand — a preset picker
(80/90/60/Off/Custom…) that writes settings.power.batteryChargeLimit via
theme-sync (--no-switch; lands on the next sys-rebuild, power.nix's oneshot
applies it). Surfaced as a first-class System row, self-gated on the
charge_control_end_threshold sysfs node like Power profile.

Moved out of the gum control-center (removed its Battery Limit case +
choose entry) so the toggle lives in one place — the rofi menu Bernardo
actually uses, per his request.

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

agent/HARDWARE-QUEUE.md

@@ -236,6 +236,13 @@ QA machine), the **T14s** (webcam case).
       unchanged (the bar still reserves its space). Accepted trade-off
       of `layer: bottom`: a floating window dragged over the top strip
       can now overlap the bar — confirm that's the only regression.
+- [ ] **Battery limit in rofi System** (iteration #64, item 36a) — after
+      `home-update`: menu › System shows a "Battery limit" row (this laptop
+      exposes the threshold node); picking a preset (80/90/60/Off/Custom)
+      writes it (`nomarchy-theme-sync get settings.power.batteryChargeLimit`
+      reflects the pick) and after a `sys-rebuild` the sysfs
+      `charge_control_end_threshold` matches. The gum control-center no
+      longer lists Battery Limit (moved, not duplicated).
 - [ ] **Config dialogs float** (iteration #63, item 41 cut) — after
       `home-update` + relogin: open Bluetooth (blueman-manager) and, if
       printing is on, System ▸ Printers (system-config-printer) — each