Codex re-gate found two issues in the uncapped-read fix: (1) open_anchored_fd
opens blocking O_RDONLY, which HANGS on a workspace FIFO/special file swapped in
at a regular-file path; (2) the non-regular fstat branch returned without
closing the fd (leak). Fix: lstat the symlink-resolved target BEFORE any open to
skip non-regular leaves (no blocking open on a FIFO), and close the fd on the
non-regular fstat branch. Adds a threaded FIFO-no-hang regression test.