vscodium: wire through HM programs.vscode so stylix can theme it

Stylix's vscode target injects workbench.colorCustomizations via the
HM programs.vscode module — it can't reach a system-package install.
Move vscodium to programs.vscode with mutableExtensionsDir = true so
GUI-installed extensions stay put, and preserve the six user settings
that aren't colour-related.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

home-manager/fred.nix

@@ -46,4 +46,19 @@ in
       cursor-style-blink = true;
     };
   };
+
+  # VSCodium — stylix's vscode target injects workbench.colorCustomizations.
+  # mutableExtensionsDir keeps GUI-installed extensions working.
+  programs.vscode = lib.mkIf isDesktop {
+    enable = true;
+    package = pkgs.vscodium;
+    mutableExtensionsDir = true;
+    profiles.default.userSettings = {
+      "window.menuBarVisibility" = "compact";
+      "window.commandCenter" = false;
+      "claudeCode.preferredLocation" = "panel";
+      "git.enableSmartCommit" = true;
+      "git.autofetch" = true;
+    };
+  };
 }

hosts/FredOS-Gaming.nix

@@ -22,7 +22,6 @@
       adwsteamgtk
       protonvpn-gui
       onlyoffice-desktopeditors
-      vscodium
       woeusb
     ];