Utility: mkdir - create a directory

Status: Built + QEMU-verified (osdev test files 11/11) - a shell built-in over the fs MKDIR API, on hierarchical GSFS (docs/persistence.md). Mutating. Trails CLAUDE.md; does not amend it.

1. What it is

mkdir <path> creates a directory. The parent directory must already exist; creating an already-existing name is a loud error, never a silent no-op (§3.12). mkdir is kept as a verb - a universal contraction, one of the two short ones we keep (cd / mkdir).

2. Usage

mkdir 0.4.0 - create a directory

usage:
  mkdir <path>        create the directory <path>
  mkdir <path> parents   create missing parent dirs too
  mkdir <a>,<b>,...   create several directories (comma-separated)
  mkdir version       print the version
  mkdir help          print this message

<path> = [index:]label/path | /abs | rel   (see docs/drives.md §4.1)

A comma list has no spaces and at most 16 items (LIST_MAX); a longer one is refused before anything is created.

3. Behaviour & bounds

mkdir allocates a directory inode and a directory block, then adds an entry to the parent (fs op 13; parents is op 18). GSFS bounds it (§26.6) with a fixed inode count overall; running out is a loud, defined error, not silent growth. (A directory is no longer one 16-entry block - see §5.) No POSIX permission bits (authority is by capability, §3.3).

Success prints created <path>. A request whose answer never came is reported as mkdir: OUTCOME UNKNOWN - <path> MAY HAVE BEEN created, not as a failure.

4. Implementation

Mutating, so the same least-authority shape as the other writers (19_write.md §4): fs holds the disk authority (Mkdir, op 13) and enforces.

5. Built / later

• mkdir <path> parents - done. Creates every missing parent directory in one call (a word, never -p, per 0_conventions.md §4); fs walks the path component by component, creating what's missing. Idempotent; errors only if a component is in the way as a file. Plain mkdir <path> stays strict (parent must exist) - parents is opt-in.
• Later: on GSFS0003 directories already grow without bound (the old 16-entry limit is gone - docs/persistence.md §6.4), so that item is moot.

6. Conformance

Conforms: mkdir help (usage with a real example per row) and mkdir version (number + creator credit) per 0_conventions.md (the shared help_block helper).