Villager profession resources and clients

The texture's .png.mcmeta supplies its hat policy:

{"villager":{"hat":"full"}}

none keeps the type layer's head visible, full hides it, and partial hides it only when the type texture has a full hat. Missing metadata means none. Pack reload refreshes the cached metadata. Unresolved saved professions retain their names and render the neutral base without a profession layer.

Clients must have the same required mods and versions. The existing configuration mod-list handshake refuses a missing mod by name before play and entity pairing. Profession owners must be required on both sides. No profession-specific packet or negotiation mechanism is added. Both sides resolve vanilla VillagerData's integer profession index against their local deterministic table. Unresolved server identities retain the existing none network projection without changing the saved identity. Shared configuration registry synchronization is follow-up work depending on #2882.