feat: overhaul config — noctalia shell, niri keybinds, battery, extra packages

- niri: switch from replaceStrings patching to plain config.kdl for simplicity
- niri: add Mod+Shift+Q (close), Mod+Shift+HJKL/Arrow (move window),
  Mod+Shift+1-9 (move to workspace)
- niri: add layer-rule to disable background-blur on noctalia bar (fix seam)
- noctalia: add capsule_group for cpu+ram (group:sysmon), panel_overlap,
  contact_shadow; corner_radius_scale 1.0
- noctalia: add all LC_* locale overrides in plasma-localerc (fix vi_VN calendar)
- system: TLP (battery), UPower, disable power-profiles-daemon (conflicts with TLP)
- system: DDC/CI support (ddcutil + i2c-dev + hardware.i2c)
- system: enable fish shell system-wide
- packages: add tree, fish, ddcutil; noctalia required services documented
- README: full rewrite with current structure, keybinds, fresh-install steps

home/modules/niri/noctalia/default.nix

@@ -20,7 +20,8 @@ in
     enable = true;
     settings = {
       bar.default = {
-        start          = [ "launcher" "clipboard" "cpu" "network" "ram" ];
+        # "group:sysmon" renders as one capsule containing cpu + ram
+        start          = [ "launcher" "clipboard" "group:sysmon" "network" ];
         center         = [ "clock" ];
         end            = [ "notifications" "volume" "brightness" "battery" "control-center" "session" ];
         thickness      = 40;
@@ -29,6 +30,16 @@ in
         margin_edge    = 0;
         margin_ends    = 0;
         widget_spacing = 8;
+
+        capsule_group = [
+          {
+            id      = "sysmon";
+            members = [ "cpu" "ram" ];
+            fill    = "surface_variant";
+            opacity = 1.0;
+            padding = 6.0;
+          }
+        ];
       };
 
       idle = {
@@ -56,12 +67,14 @@ in
       shell = {
         font_family         = "JetBrainsMono Nerd Font";
         polkit_agent        = true;
-        corner_radius_scale = 0.0;
+        corner_radius_scale = 1.0;
         animation.speed     = 1.5;
         panel = {
           clipboard_placement     = "attached";
           launcher_placement      = "attached";
           launcher_session_search = true;
+          panel_overlap           = 1;    # pull panel flush against bar to hide seam
+          contact_shadow          = true; # gradient at meeting point masks any residual gap
         };
         shadow.alpha = 0.5;
       };