docs(install): clarify verification step

Match README wording: "Launch Claude Code and run /gsd:help"

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

bin/install.js

@@ -164,7 +164,7 @@ function install(isGlobal) {
   console.log(`  ${green}✓${reset} Installed get-shit-done`);
 
   console.log(`
-  ${green}Done!${reset} Run ${cyan}/gsd:help${reset} to get started.
+  ${green}Done!${reset} Launch Claude Code and run ${cyan}/gsd:help${reset}.
 `);
 }