Every lowercase identity constant is now derived from a single _SLUG, so
a rename is one edit. The values are unchanged (checked against
origin/main for all 33 constants and the user agent).
legacy_import: drop the unused subdirectory field from the payload
tuples, merge the four near-identical directory helpers, and use the
identity constants directly instead of aliases.
Docstrings: the retained package is vocalinux, not voculinux; the
one-time import is described as a legacy Vocalinux install.