- Implement OBJ_LIST with offset-based items array and capacity
- obj_free now releases child allocations (string buffer, list items)
- obj_print detects self-referencing lists to prevent infinite recursion
- Visualizer distinguishes freed blocks (JLANG_NOT_USE) from active ones
- JLANG_free now zeroes payload on release
JLANG_malloc now returns size_t offsets relative to the heap buffer,
making all references stable across heap growth (realloc). Object API
updated accordingly: constructors return offsets, obj_print/obj_free
receive (allocator, offset). Added heap auto-grow when out of space.
