feat: implicit return for single expressions using acorn parser

- Parse code with acorn to detect single expression statements
- Auto-wrap expressions with 'return await (...)' for implicit return
- Exclude side-effects: assignments, updates (x++), delete operator
- Update skill.md examples to remove console.log (keep await)
- Add unit tests for shouldAutoReturn function

pnpm-lock.yaml

@@ -86,6 +86,9 @@ importers:
       '@xmorse/cac':
         specifier: ^6.0.7
         version: 6.0.7
+      acorn:
+        specifier: ^8.15.0
+        version: 8.15.0
       async-sema:
         specifier: ^3.1.1
         version: 3.1.1