docs(backlog): fold Bernardo's power-menu mockup into item 36(b)

He supplied a reference `power-menu` rofi script (battery charge + power
profile rows, icon protocol, notify-send). Un-gates the design hold on
36(b): records the shape + the Nomarchy adaptation (reuse the existing
batterylimit/power-profile writers instead of raw TLP; wire the Waybar
battery module on-click). One [human] call left: replace the separate
System rows or keep both surfaces.

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

agent/BACKLOG.md

@@ -31,10 +31,23 @@ next, in what order*.
 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) `[human]` **Battery-icon click → a dedicated power menu** offering
-  charge threshold + power profile (and switching backend to TLP when
-  relevant). Bernardo will provide a mockup ("when it's time") — hold
-  design until then. Pairs with the instant-effect follow-up in PROPOSED.
+- (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