feat: add netssh version and --version

`netssh --version` used to be passed to ssh and failed with
"unknown option -- -". Release builds now embed the tag via
-X main.version; other builds fall back to the module build info.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/netssh/main.go

@@ -40,6 +40,7 @@ var managedSubcommands = map[string]bool{
 	"completion": true,
 	"__complete": true,
 	"help":       true,
+	"version":    true,
 }
 
 func main() {
@@ -49,6 +50,10 @@ func main() {
 		runTUI()
 		return
 	}
+	if args[0] == "--version" {
+		fmt.Printf("netssh %s\n", buildVersion())
+		return
+	}
 
 	if managedSubcommands[args[0]] {
 		if err := rootCmd().Execute(); err != nil {
@@ -352,7 +357,7 @@ func rootCmd() *cobra.Command {
 		},
 	}
 
-	root.AddCommand(notesCmd(), configureCmd(), searchCmd(), cacheCmd(), aliasCmd(), hookCmd(), shellInitCmd())
+	root.AddCommand(notesCmd(), configureCmd(), searchCmd(), cacheCmd(), aliasCmd(), hookCmd(), shellInitCmd(), versionCmd())
 
 	// cobra builds the "completion" command lazily; force init so we can extend it.
 	root.InitDefaultCompletionCmd()