feat(waybar): combined power menu on the battery + profile icons

Item 36(b). Adds `nomarchy-menu powermgmt` — one flat rofi menu of power
Profile rows (→ powerprofilesctl set) + Charge limit rows (→ the same
theme-sync writer batterylimit uses), each half self-gating on its
hardware. No backend duplication; Custom charge stays in the dedicated
batterylimit picker.

Opened two ways (Bernardo's call): the Waybar battery icon AND the
power-profile icon — the profile icon's click flips from cycle → menu.
Wired in waybar.nix and all four whole-swaps (parity). Named `powermgmt`
to avoid the whole-swaps' existing `custom/powermenu` shutdown button
(→ nomarchy-menu power), which is left untouched. The granular System ▸
Power profile / Battery limit rows stay ("keep both").
nomarchy-powerprofile-cycle kept as a standalone bin, now unbound by
default.

Verified: V0 green; V1 HM built (bash -n) — powermgmt case ships, the
generated waybar-config.json wires both icons (2 hits), all four jsoncs
re-wired and still parse, shutdown buttons intact. Click→menu→apply is
V3 (queued).

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

agent/BACKLOG.md

@@ -26,29 +26,6 @@ next, in what order*.
 
 ## NEXT
 
-### 36. Battery / power quick menu `[human]`
-(Raised by Bernardo, 2026-07-07 — item 6.) Slice (a) — the charge-threshold
-toggle in the rofi System submenu — shipped 2026-07-07 (iteration #64;
-`nomarchy-menu batterylimit`, self-gated on the sysfs node, and MOVED out
-of the gum control-center). Remaining:
-- (b) **Battery-icon click → a dedicated power menu** offering charge
-  threshold + power profile. Mockup provided by Bernardo 2026-07-08 (a
-  `power-menu` rofi script from another system): a `rofi -dmenu` with
-  icon'd rows via the `\x00icon\x1f<name>` protocol — "Charge to 100%",
-  "Limit to 80%" (battery-*-charging-symbolic icons) + power-profile rows
-  (power-profile-{power-saver,performance}-symbolic), each `case` firing a
-  backend command + `notify-send`. The submitted script drives **TLP**
-  (`tlp fullcharge` / `tlp setcharge 75 80 BAT0`) and ryzenadj (ignore the
-  ryzenadj half). **Nomarchy adaptation:** reuse the existing writers, not
-  raw TLP — charge rows call `nomarchy-menu batterylimit`'s logic
-  (sysfs `charge_control_end_threshold` + baked `settings.power.
-  batteryChargeLimit`), profile rows call `power-profile`'s (PPD). Wire the
-  Waybar **battery module `on-click`** (generated `waybar.nix` + all four
-  whole-swap jsoncs — parity) to a new `nomarchy-menu powermenu`. Open
-  call left: whether to *replace* the separate System ▸ Battery limit /
-  Power profile rows or keep both surfaces. Pairs with the instant-effect
-  follow-up in PROPOSED (a udev grant makes the charge write no-rebuild).
-
 ### 29. Laptop docking / external-monitor UX `[human]` (needs hardware)
 (Raised by Bernardo, 2026-07-07.) The shipped display application is
 weak and unintuitive, and Hyprland's model for workspaces across