feat: show subcommands after hostnames in shell completion

Use ShellCompDirectiveKeepOrder so fish/zsh/bash preserve the returned
order instead of sorting alphabetically. ValidArgsFunction now appends
subcommand names (with their short descriptions) after all hostname
entries, so hosts always appear first in the completion list.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/netssh/main.go

@@ -199,12 +199,18 @@ func rootCmd() *cobra.Command {
 			}
 			c := cache.New(cfg.Cache.Path, cfg.Cache.TTL)
 			_ = c.Load()
-			entries := c.Search(toComplete)
-			names := make([]cobra.Completion, len(entries))
-			for i, e := range entries {
-				names[i] = cobra.Completion(e.Name)
+
+			var completions []cobra.Completion
+			for _, e := range c.Search(toComplete) {
+				completions = append(completions, cobra.Completion(e.Name))
 			}
-			return names, cobra.ShellCompDirectiveNoFileComp
+			// Subcommands at the end, after all hostnames.
+			for _, sub := range cmd.Commands() {
+				if sub.IsAvailableCommand() && strings.HasPrefix(sub.Name(), toComplete) {
+					completions = append(completions, cobra.Completion(sub.Name()+"\t"+sub.Short))
+				}
+			}
+			return completions, cobra.ShellCompDirectiveNoFileComp | cobra.ShellCompDirectiveKeepOrder
 		},
 	}