Adds a `nomarchy.system.power.*` surface (modules/nixos/power.nix),
replacing the bare `services.upower` (Waybar reporting only) baseline:
- power-profiles-daemon ships by default; switched through polkit (no
root prompt). TLP is the opt-in `backend = "tlp"` for deeper battery
tuning — the two are mutually exclusive (asserted).
- thermald behind `power.thermal.enable` (Intel-only).
- `power.batteryChargeLimit` (e.g. 80): a backend-independent sysfs
oneshot writes charge_control_end_threshold; gated on `power.laptop`.
Switcher + indicator live home-side and self-gate on a battery being
present + powerprofilesctl running, so they hide on desktops and under
TLP — no system->home wiring (like the Waybar battery widget):
- rofi.nix: `nomarchy-menu power-profile` module + a picker entry shown
only on laptops with PPD.
- waybar.nix: first `custom/*` module — click cycles the profile.
Installer writes `power.laptop = true` (battery probe) and
`power.thermal.enable` (GenuineIntel) into the generated system.nix, and
scaffolds the charge limit commented-out.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>