Add GNU-style copyright to version output, project URL to help

Attribution follows the coreutils convention: license and authorship
live in version output where they read as rights information, not in
help where they would be noise. The help footer gains the project URL
for bug reports.

Author: usmanbashir

main.go

@@ -223,7 +223,11 @@ func cmdCompletions(args []string) {
 	}
 	fmt.Print(s)
 }
-func cmdVersion() { fmt.Println("clau " + versionString()) }
+func cmdVersion() {
+	fmt.Println("clau " + versionString())
+	fmt.Println("Copyright (C) 2026 Usman Bashir. License GPL-3.0-or-later.")
+	fmt.Println("https://github.com/usmanbashir/clau")
+}
 func cmdHelp()    { fmt.Print(helpText) }
 
 const helpText = `clau — model×effort shortcodes and launch profiles for Claude Code
@@ -245,4 +249,5 @@ Management (clau only):
   clau version | help
 
 Config: $CLAU_CONFIG or ~/.config/clau/config.toml
+Project: https://github.com/usmanbashir/clau
 `