Utility: `rename` - rename a file or directory in place

Status: Built + QEMU-verified (osdev test files 15/15) - a shell built-in over the fs RENAME op, which edits the directory entry in place (no reclamation needed). On hierarchical GSFS (docs/persistence.md). Trails CLAUDE.md; does not amend it.

1. What it is

rename <path> <newname> changes the name of a file or directory, in the same directory - it does not move it. This is the half of POSIX mv that is purely a name change; relocation is move (22_move.md). Splitting the two is the explicit GodspeedOS way (§26.5), and it mirrors drives label, which renames a drive - same idea, one level up.

2. Usage

rename 0.4.0 - rename an entry in place

usage:
  rename <path> <newname>   rename <path> to <newname>
  rename version            print the version
  rename help               print this message

<path>    = [index:]label/path | /abs | rel   (see docs/drives.md §4.1)
<newname> = a single name component (no '/')

3. Behaviour

rename rewrites the directory entry's name in place - no blocks are read or freed, so it is cheap and reclamation-free. <newname> is one component: fs refuses a slash or a control byte (rename: failed - bad new name) - to move across directories, use move. Renaming to a name that already exists in the directory is a defined error (rename: failed - name already exists), not an overwrite. Success prints renamed <path> → <newname>; a request whose answer never came prints rename: OUTCOME UNKNOWN - ... and is not re-sent.

4. Implementation

Mutating, least-authority shape of the writers (19_write.md §4): fs edits the parent directory block (RENAME, op 15) and persists it.

5. Later (separate doc so it can grow)

Case/charset rules for names, once a real need surfaces.
Bulk rename / patterns - only if a genuine use pulls it in (§26.2).

6. Conformance

Built spec-first against 0_conventions.md: implements its own rename help / rename version.

GodspeedOS

Utility: rename - rename a file or directory in place