Add netty worktree helpers

Add netty-specific worktree helper commands and a zsh wrapper that creates sibling worktrees and cds into them.

Also split script packaging so Darwin keeps the existing wt integration while netty gets git-worktree-based helpers.

Co-authored-by: Codex <noreply@openai.com>

home/netty.nix

@@ -1,6 +1,6 @@
-{ ... }:
-{
+{...}: {
   imports = [
     ./common.nix
+    ./netty-worktree.nix
   ];
 }