AWK codegen:
- Add string interpolation: "Hello {name}" -> ("Hello " name "!")
- Add env.VAR support via ENVIRON["VAR"]
- Add time.now() via systime()
- Add str.chr() via sprintf("%c", n)
- Add assert_eq() for equality assertions
- Add print() as statement
- Add method calls as statements (arr.push, dict.set)

Bash codegen:
- Fix dict.field = value for dict variables (was using wrong storage)
- Fix dict.field read to use dict["field"] syntax