Deploy a reusable image generator that skills reference to produce
images from a chosen model: creates it or appends a version.
An image generator is a named, versioned configuration that routes
image generation calls to a specific model. Generators are private and
owner-scoped. Skills reference them by UUID or ``uuid@version``.
You cannot deploy a new generator whose ``name`` matches an active
platform ``scope=system`` generator (those are tier-level configs
that are run-only and not listed or fetched).
Versioning: the first deploy with a given ``name`` creates the
generator at version 1. Re-deploying the same ``name`` appends a new
version and requires ``expected_version_token`` from the latest known
version (returned by deploy/list/get). A new generator must omit the
token; an existing one without a token returns Conflict.
Deploy-time validation: the ``model`` is checked against the pricing
layer. A model that does not resolve to a known image endpoint with an
authoritative price is rejected before any row is written.
Returns: ``{generator_id, name, description, current_version, version,
version_token, status, scope, provider, model, generation_contract,
config_hash, created_at}``. Persist ``version_token`` for the next
re-deploy.
