feat(mc): add midnight commander with declarative config

Public baseline module: installs `mc` plus `ouch` (backs the F2 pack/unpack
entries, archive format inferred from the extension), and ships `ini`, `menu`,
and a generated `panels.ini` into `$XDG_CONFIG_HOME/mc`.

`local.mc.otherDir` exposes the other-panel start dir as an option defaulting
to `config.home.homeDirectory`, so the one personal value isn't baked in. The
F2 user menu is trimmed to the entries that match this config (imv/zathura/mpv
openers, ouch pack/unpack, man view); the stock rcp/uudecode/news/latex cruft
is dropped. `auto_save_setup=false` keeps mc from rewriting the read-only store
symlinks on exit.

modules/home.nix

@@ -71,7 +71,7 @@ let
   '';
 in
 {
-  imports = [ ./gpg.nix ./media.nix ./texlive.nix ./librewolf.nix ];
+  imports = [ ./gpg.nix ./media.nix ./texlive.nix ./librewolf.nix ./mc.nix ];
 
   # Put ~/.local/bin (the XDG user-bin dir) on PATH so hand-dropped scripts run
   # by name without wiring each through nix.