- Add proper type tracking for function and method parameters
- DCE now tracks array-returning methods (keys, split, slice)
- Fix split/slice to return arrays via __CT_RET_ARR
- Add foreach support for inline split expressions
- Detect object parameters by unknown method calls
- Add comprehensive tests for parameter passing

New test classes:
- TestFunctionParameterPassing (11 tests)
- TestClassInstancePassing (4 tests)