`_fd_is_truly_unlinked` stats `/proc/<pid>/fd/<n>` after the scan has
already read the readlink target. Between those two steps the descriptor
can be closed (ENOENT, handled by the previous commit) or the whole
process can exit (ESRCH). Both mean the descriptor can no longer keep a
retired WAL/SHM generation alive, so neither is evidence of a live holder
and neither should make the guard refuse to open the database.
Match the sibling scan in hermes_state_holders, which already skips both
errnos, by branching on `exc.errno in (ENOENT, ESRCH)`; any other OSError
still fails closed. The existing closed-descriptor test is parametrized
over both errnos, injecting the failure at `os.stat` so the ESRCH path is
exercised on every platform.
kshitijk4poor
7feaf03883