The old file_path response field was a namespaced storage locator
(models/checkpoints/foo.safetensors): not an absolute path, not unique
identity, and not the value a loader consumes. Nothing needs that shape
on the wire (hash/ID-based locating is the long-term direction), so it
is dropped rather than renamed; the storage-root matching stays internal,
powering display_name.
What loaders DO need is the in-root loader path (category dropped:
models/checkpoints/foo/bar.safetensors -> foo/bar.safetensors). Serve it
as a first-class loader_path field, persisted on asset_references
(migration 0006) and written by every ingest pipeline at insert, so
responses read the column verbatim.
Like the model_type tags, loader_path is a seed-time derivative of the
model folder registry, maintained by the same scan lifecycle (new files seed
fresh values, pruning retires rows whose bucket disappeared). Rows
predating the column serve a null loader_path; databases from before
this stack already need recreating for the base branch's tag changes.
loader_path resolves every registered base including extra_model_paths
entries; display_name only the canonical storage roots. A file can
therefore be loadable with no display name (extra-path models) or the
reverse (unregistered files under the models root), and loader_path is
null exactly when no loader can resolve the file.
