Problem: selene flagged unused err3 variable, and test mock_enums
still mocked io.open instead of the new vim.uv.fs_* calls.
Solution: rename err3 to _, replace io.open mock with synchronous
vim.uv.fs_open/fs_fstat/fs_read/fs_close mocks using a sentinel fd.
Problem: parse_enums read the bash-completion file with blocking
io.open/fd:read on the main thread, stalling the event loop.
Solution: read the file via vim.uv.fs_open/fstat/read with callbacks,
running in parallel with the ghostty config system call using the
same remaining-counter pattern as the other blink-cmp plugins.
