#292 funcl has no DIRECTORY (directory enumeration / getdents) — blocks asdf load-system system search

asdf's system searchers (sysdef-central-registry-search, sysdef-source-registry-search) need to enumerate a directory to find .asd. funcl has no directory function and no getdents syscall — grep finds only directory-namestring (pathname string munging). Calling directory yields UNDEFINED-DESIGNATOR: DIRECTORY (masked as NIL under ignore-errors), so every searcher misses and load-system returns 'system not found'. probe-file works, so central-registry with an explicit .asd would resolve, but the search path itself calls directory.

Need: implement CL directory (and uiop:directory-files/directory*): open(dir, O_DIRECTORY) + getdents64 (x86-64 syscall 217) loop + dirent parse (d_reclen, d_name) + wildcard match + pathname construction. This is the last blocker before a baked (or fresh) funcl-asdf can resolve and load-system a real system; cave#209 (segfault) and cave#291 (condition persistence) are already fixed.