feat(librewolf): expose package as an overridable option

Move librewolf out of the bare package list into its own module declaring
`local.librewolf.package` (default pkgs.librewolf), mirroring texlive. Lets a
consumer swap the wrapped package — extraPolicies/extraPrefs — to share
extensions and an about:config baseline across profiles without editing the
module.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home.nix

@@ -71,7 +71,7 @@ let
   '';
 in
 {
-  imports = [ ./gpg.nix ./media.nix ./texlive.nix ];
+  imports = [ ./gpg.nix ./media.nix ./texlive.nix ./librewolf.nix ];
 
   # Put ~/.local/bin (the XDG user-bin dir) on PATH so hand-dropped scripts run
   # by name without wiring each through nix.
@@ -119,7 +119,8 @@ in
   xdg.enable = true;
 
   home.packages = with pkgs; [
-    librewolf
+    # librewolf is installed by ./librewolf.nix (via local.librewolf.package) so
+    # the wrapped package stays overridable — do NOT also list it here.
     keepassxc   # config in ~/.config/keepassxc
     papirus-icon-theme   # fuzzel icon-theme; ships non-symbolic power icons
                          # (Adwaita only has them as symbolic, which fuzzel skips)