feat: live charge limit, identity retunes, btop assets (product calls)

- Charge limit: udev GROUP=users on threshold; menu applies sysfs live
  and persists state; boot/AC oneshot prefers live theme-state.json.
- Look & Feel: Reset wallpaper (auto); Theme/next/night light already there.
- NVIDIA first-class wrappers deferred past v1 (keep #59 comments).
- Identity taste: white, lumon, hackerman, matte-black, miasma.
- Hand btop.theme for identity + boreal/executive-slate/neon-glass.

Verified: V0 contrast; V1 battery-charge-limit VM. V3 live sysfs on laptop.

modules/nixos/options.nix

@@ -109,9 +109,10 @@
           where the hardware exposes charge_control_end_threshold on a
           system battery (type=Battery under /sys/class/power_supply;
           name-agnostic — BAT0, CMB0, …).
-          null leaves charging at the firmware default. Backend-independent
-          (a small systemd unit writes the sysfs knob, re-applied on AC
-          state changes), so it works under PPD too; needs
+          null leaves charging at the firmware default (menu writes 100).
+          Backend-independent: the menu applies live via sysfs (udev
+          GROUP=users on the threshold node) and persists settings in
+          theme-state; a oneshot re-applies on boot and AC replug. Needs
           nomarchy.system.power.laptop.
         '';
       };