feat(waybar): explain 'Not charging' hold state in the battery tooltip

With a charge cap, AC-plugged inside the hysteresis band (power.nix:
start = cap − 10) reports 'Not charging' — indistinguishable from a
broken charger without a hint. tooltip-format-plugged now says the cap
is holding the level and how charging resumes. No cap value baked: the
menu changes it live without a rebuild.

Whole-swap parity: the same tooltip added to all four theme
waybar.jsonc files (boreal/executive-slate/summer-day/summer-night) —
the generated config is bypassed under these themes.

Verified on hardware (TuringMachine, boreal theme, cap 80, battery 71%
in the hold band): all four jsonc validate with jq; home-manager switch
deploys the boreal config with the tooltip; battery currently in the
exact Plugged state the tooltip targets.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

modules/home/waybar.nix

@@ -265,6 +265,13 @@ let
       format = "<span size='${toString (t.fonts.size + 2)}pt'>{icon}</span>{capacity}%";
       format-charging = "<span size='${toString (t.fonts.size + 2)}pt'>󰂄  </span>{capacity}%";
       format-icons = [ "󰁺  " "󰁼  " "󰁾  " "󰂀  " "󰁹  " ];
+      # The kernel's "Not charging" maps to waybar's Plugged state — on a
+      # machine with a charge cap that's the hold band doing its job
+      # (power.nix sets start = cap − 10), which reads as "broken charger"
+      # without an explanation. The cap value isn't baked here: the menu
+      # can change it live (sysfs + state, no rebuild), so a number would
+      # go stale.
+      tooltip-format-plugged = "Plugged in, not charging — held at {capacity}% by the battery charge cap\nCharging resumes ~10% below the cap · click to adjust";
       # Click either the battery or the power-profile icon → the combined
       # power menu (profile + charge cap). The granular System rows stay.
       on-click = "nomarchy-menu powermgmt";