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>

scripts/wt-create.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+if [[ $# -ne 1 ]]; then
+  printf 'usage: wt-create <worktree-name>\n' >&2
+  exit 1
+fi
+
+branch_name=$1
+repo_root=$(git rev-parse --show-toplevel 2>/dev/null) || {
+  printf 'wt-create: not inside a git repository\n' >&2
+  exit 1
+}
+
+target_path=$(wt-path "$branch_name")
+
+if [[ -e "$target_path" ]]; then
+  printf 'wt-create: path already exists: %s\n' "$target_path" >&2
+  exit 1
+fi
+
+if git -C "$repo_root" show-ref --verify --quiet "refs/heads/$branch_name"; then
+  git -C "$repo_root" worktree add -- "$target_path" "$branch_name" 1>&2
+else
+  git -C "$repo_root" worktree add -b "$branch_name" -- "$target_path" HEAD 1>&2
+fi
+
+printf '%s\n' "$target_path"