fix(macos): bring in macOS ui_api.cpp with all mac_ helper definitions

The upstream macos/issue-8-sync-smoke-merge branch adds ~1050 lines of
macOS-specific helpers to ui_api.cpp that are declared in ui_main.h but
were missing from our branch, causing linker errors:

  mac_module_is_misc, mac_build_pload_data_tail_chunk,
  mac_run_module_chunk_fresh_co, mac_lua_load_module_file,
  mac_try_bisect_global_module, mac_try_bisect_misc_module,
  mac_pload_module_pcall, and related slice/bisect infrastructure.

Replace our base (non-macOS) ui_api.cpp with the fully patched version.
Additional includes: sstream, vector, climits, cstdlib, cstring, string.

https://claude.ai/code/session_01E69xvgJuYgUaR1eHY3Qf3o

Author: claude