fix(darwin+HM): align nixpkgs↔nix-darwin, force HM home path, dedupe nvim/tmux 🔧

- track nixpkgs at `github:NixOS/nixpkgs/nixpkgs-unstable` to pair with
  `nix-darwin/master`
- update lockfile inputs: flake-compat, home-manager, NixOS-WSL,
  nixpkgs, nixos-vscode-server
- darwin: wrap HM module in a function to access `lib` and
  `mkForce` `home.homeDirectory = "/Users/danny"` (and set username) to
  satisfy HM’s absolute-path requirement under root activation
- HM: comment out duplicated `home.username` / `home.homeDirectory` in
  `home/danny/home.nix`
- HM: remove `neovim` and `tmux` from `home.packages` (managed via
  `programs.*`), fixing conflicting `nvim` subpath error

nixos/home/danny/home.nix

@@ -1,7 +1,8 @@
 { pkgs, ... }:
 {
-  home.username = "danny";
-  home.homeDirectory = "/Users/danny";
+  # TODO: remove next two lines from here or from flake.nix
+  # home.username = "danny";
+  # home.homeDirectory = "/Users/danny";
 
   programs.home-manager.enable = true;
 
@@ -121,11 +122,9 @@
     ];
   };
 
-  # Put user-installed binaries here if you want HM to own them (optional)
-  home.packages = with pkgs; [
-    neovim
-    tmux
-  ];
+  # TODO: Put user-installed binaries here if you want HM to own them (optional)
+  # home.packages = with pkgs; [
+  # ];
 
   # First HM version for this user config; bump only if you understand the migration notes.
   home.stateVersion = "24.11";