Name a real transform, and pin the names to damrs

Name a real transform, and pin the names to damrs The media source fetched its thumbnail with `w=320,h=320,fit=inside,fmt=webp`, written on the assumption that a transform describes an image. It does not. `delivery::op_hash_for` resolves a transform against the built-in profiles and then the tenant's conversions, and anything else is NotDeliverable — deliberately, because approximating a typo'd profile would silently hand back a different size than the caller integrated against. So every thumbnail this module fetched would have been refused, on every request, and nothing on the Drupal side would have said why: the fetch failure path logs a notice and falls back to the generic icon, which is exactly the behaviour a restricted asset produces. It would have looked like a rights problem forever. The valid names are original, thumb-256, preview-1024 and web-2048, plus a tenant's conversion keys. They are now a Transforms class pinned to a fixture generated by `cargo run -p dam-media --example transform_names`, and CI diffs that fixture the same way it diffs the signing vectors. A rename upstream fails the connector's tests rather than its users' pages. The example lives in dam-media rather than dam-core, because dam-core cannot depend on dam-media without a cycle. Found by reading the delivery path to write the next submodule, not by any test — the module's own suite was green, since a fixture cannot know that the string it signs is meaningless.