fix: remove doubled .kugetsu-worktrees path segment in issue_ref_to_worktree_path

Fixes #179 - cmd_start fails due to incorrect worktree path being created
with .kugetsu-worktrees/.kugetsu-worktrees/ instead of just the worktree name.

skills/kugetsu/scripts/kugetsu-worktree.sh

@@ -10,7 +10,7 @@ issue_ref_to_worktree_path() {
     local issue_ref="$1"
     local parent_dir="${2:-$WORKTREES_DIR}"
     local worktree_name=$(issue_ref_to_worktree_name "$issue_ref")
-    echo "$parent_dir/.kugetsu-worktrees/$worktree_name"
+    echo "$parent_dir/$worktree_name"
 }
 
 issue_ref_to_branch_name() {