home: centralize theme and make home-manager feature-aware

- add home/theme.nix as the single Silicon Volt palette and pass it to
  home modules via extraSpecialArgs
- drive foot, hyprland, hyprlock, mako, fzf, starship, rofi and the
  herdr picker from that palette; raw config files use @color@ tokens
  substituted at build time
- pass my = config.my into home-manager; add my.pi.enable, my.flakeDir
- gate home/pi.nix on my.pi.enable (enabled on hades)
- route zshconf/hyprconf aliases and FLAKE_CONFIG through my.flakeDir
- rename the hyprland monitor option volt.monitors -> hypr.monitors
- fix use_auto_tmux command-substitution bug in zsh/init.zsh
- track home/nvim/config/lazy-lock.json for reproducible plugins
- document theming and toggles in the README

home/scripts/herdr-picker.sh

@@ -48,9 +48,9 @@ if command -v fzf &>/dev/null; then
     --layout=reverse \
     --border=rounded \
     --prompt="  Herdr Session > " \
-    --color=fg:#e5e2e1,bg:#131313,hl:#CFFC00,fg+:#ffffff,bg+:#1c1b1b,hl+:#e3ff66 \
-    --color=info:#ADAAAA,prompt:#CFFC00,pointer:#FF7A59,marker:#CFFC00,spinner:#00BFFF \
-    --color=border:#2a2929,gutter:#131313 \
+    --color=fg:@fg@,bg:@bg@,hl:@volt@,fg+:@fgBright@,bg+:@glass@,hl+:@voltLight@ \
+    --color=info:@muted@,prompt:@volt@,pointer:@coral@,marker:@volt@,spinner:@blue@ \
+    --color=border:@surface@,gutter:@bg@ \
     --header="Select Herdr session to attach / create | Esc for plain shell" \
     --header-first)
 else