Apply macro expansion to teardown commands and fix @def continuation parsing

Teardown commands were missing the expandMacro call that setup and
parsed commands already received. Also relax the continuation-line
guard to catch bare `$` (not just `$ `) so lines like `$VAR` are
not silently consumed as continuation text.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli/index.ts

@@ -150,7 +150,7 @@ program
         commands: [
           ...setupCommands.map(expandMacro),
           ...parsed.commands.map(expandMacro),
-          ...teardownCommands,
+          ...teardownCommands.map(expandMacro),
         ],
       }