theming: stop the server repainting SSH clients' terminal palette

base16-fish and stylix's btop theme were only disabled on desktops, so a
login shell on Mediaserver printf'd OSC 4/10/11 back down the SSH pipe and
overwrote the client's wallpaper palette. Off everywhere, server TUIs draw
in the client's 16 ANSI colours instead.

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

settings/theming.nix

@@ -541,40 +541,49 @@ in
     apply = lib.mkOption { internal = true; type = lib.types.path; };
   };
 
-  config = lib.mkIf isDesktop {
+  config = lib.mkMerge [{
+    # EVERY host, servers included. stylix ships fish as BOTH a NixOS and a
+    # home-manager target, and this is the NixOS half —
+    # programs.fish.interactiveShellInit in /etc/fish. Turning off only the
+    # home-manager one left this still sourcing base16-fish, which printf's
+    # OSC 4 / OSC 10 / OSC 11 at every shell start and repaints the build-time
+    # palette over whatever ghostty just reloaded. Both halves have to go or
+    # the terminal never changes colour.
+    #
+    # Why this is not desktop-only: OSC escapes repaint the terminal that
+    # DISPLAYS the shell, not the machine running it. A login shell on the
+    # server sends them straight back down the SSH pipe, so sshing into
+    # Mediaserver from a themed ghostty repainted the local window in the
+    # server's build-time wallpaper colours. Off, the server touches nothing
+    # and every TUI over SSH just uses the client's 16 ANSI colours — which
+    # theme-apply already keeps in sync with the wallpaper. No theme state
+    # has to cross the wire at all.
+    stylix.targets.fish.enable = false;
+    home-manager.users.fred.stylix.targets.fish.enable = false;
+
+    # Same story for btop, one app instead of the whole palette: stylix would
+    # write a hex theme baked from the host's own wallpaper. On a desktop
+    # theme-apply owns that file (color_theme points at the state symlink
+    # below); on the server there is no wallpaper worth following, so leaving
+    # color_theme unset lands on btop's built-in Default, which draws in the
+    # terminal's 16 ANSI colours and therefore in the client's theme.
+    home-manager.users.fred.stylix.targets.btop.enable = false;
+  }
+  (lib.mkIf isDesktop {
     fred.theming = {
       inherit walls defaultWall;
       apply = themeApply;
     };
 
-    # stylix ships fish as BOTH a NixOS and a home-manager target, and this is
-    # the NixOS half — programs.fish.interactiveShellInit in /etc/fish. Turning
-    # off only the home-manager one left this still sourcing base16-fish, which
-    # printf's OSC 4 / OSC 10 / OSC 11 at every shell start and repaints the
-    # build-time palette over whatever ghostty just reloaded. Both halves have
-    # to go or the terminal never changes colour.
-    stylix.targets.fish.enable = false;
-
     home-manager.users.fred = { config, lib, pkgs, osConfig, ... }: {
-      # These four targets write build-time files that theme-apply replaces
+      # These targets write build-time files that theme-apply replaces at
-      # at runtime; leaving them on means stylix and the switcher fight over
+      # runtime; leaving them on means stylix and the switcher fight over the
-      # the same paths on every rebuild.
+      # same paths on every rebuild. (btop's is off for every host above.)
       stylix.targets.gtk.enable = false;
       stylix.targets.ghostty.enable = false;
-      stylix.targets.btop.enable = false;
 
-      # The one that made ghostty look unthemeable. stylix's fish target
+      # (fish's two targets are killed for every host above — base16-fish is
-      # sources base16-fish, which is a base16-SHELL script: at every shell
+      # what made ghostty look unthemeable, locally and over SSH alike.)
-      # start it printf's OSC 4 (palette 0-15) and OSC 10/11 (fg/bg) with the
-      # BUILD-TIME colours, overwriting whatever ghostty just loaded. So a
-      # wallpaper switch reloaded ghostty correctly and fish immediately
-      # painted the old scheme back over it — and opening a new window ran
-      # fish again, which is why reopening never helped either. Only
-      # selection-background, which base16-fish does not touch, got through.
-      #
-      # Off, fish leaves the palette alone and inherits the terminal's, so
-      # every ANSI-coloured program in a ghostty window follows a switch live.
-      stylix.targets.fish.enable = false;
 
       # Same reasoning, one layer up: stylix's yazi target writes a theme in
       # hex, which would pin yazi to the build-time scheme. home-manager/
@@ -622,5 +631,5 @@ in
       programs.ghostty.settings.keybind = [ "ctrl+shift+alt+f12=reload_config" ];
       programs.btop.settings.color_theme = "${stateLink}/btop.theme";
     };
-  };
+  })];
 }