fix(kratos): make Android Mosh app work with nushell login shell

The old Android Mosh app discovers mosh-server via POSIX shell idioms
(command -v / type) through the user's login shell. Nushell has no
command/type builtins and which prints a table, so the app reported
'mosh-server Not Found' on kratos (user shell: nu) while working on
hermes (app logs in as bash user).

Fix: use bash as login shell on kratos and exec into nushell for
interactive login sessions via programs.bash.interactiveShellInit.
Non-interactive SSH exec (app bootstrap, Termux mosh) stays in bash
where POSIX semantics work.

Also fixes the stale nh flake path (p/nixos -> p/NIX).

hosts/m3-kratos/configuration.nix

@@ -70,6 +70,12 @@
 
   # Define a user account. Don't forget to set a password with ‘passwd’.
 
+  # bash as login shell wrapper: non-interactive SSH clients (e.g. the
+  # Android Mosh app bootstrap, which runs `command -v mosh-server`)
+  # need POSIX shell semantics. Interactive login sessions exec into
+  # nushell automatically — see programs.bash in ./programs.nix.
+  users.users.m3tam3re.shell = pkgs.bashInteractive;
+
   # List packages installed in system profile. To search, run:
   # $ nix search wget
   environment.systemPackages = with pkgs; [neovim git];

hosts/m3-kratos/programs.nix

@@ -32,6 +32,19 @@
     ];
   };
   programs.fish.enable = true;
+  # Login shell is bash (see configuration.nix), but interactive login
+  # sessions exec straight into nushell. Non-interactive SSH commands
+  # (e.g. the Android Mosh app bootstrap `command -v mosh-server`)
+  # stay in bash where POSIX shell semantics work.
+  programs.bash = {
+    enable = true;
+    interactiveShellInit = ''
+      if [[ $- == *i* ]] && shopt -q login_shell && [[ -z "''${M3_SHELL_TO_NU:-}" ]]; then
+        export M3_SHELL_TO_NU=1
+        exec ${pkgs.nushell}/bin/nu --login
+      fi
+    '';
+  };
   programs.thunar = {
     enable = true;
     plugins = with pkgs; [thunar-archive-plugin thunar-volman];
@@ -46,6 +59,7 @@
     enable = true;
     clean.enable = true;
     clean.extraArgs = "--keep-since 4d --keep 3";
-    flake = "/home/m3tam3re/p/nixos/nixos-config";
+    flake = "/home/m3tam3re/p/NIX/nixos-config";
   };
+  programs.mosh.enable = true;
 }