feat(cli): default bare flynn invocation to tui

src/cli/index.ts

@@ -76,5 +76,8 @@ function isDirectRun(): boolean {
 
 if (isDirectRun()) {
   const program = createProgram();
-  program.parse(process.argv);
+  const argv = process.argv.length <= 2
+    ? [...process.argv, 'tui']
+    : process.argv;
+  program.parse(argv);
 }