Tree/category field options

Creates a metadata-only resource of the named type, optionally setting field values in the same call. Requires the `write` scope. ### Names, not refs `type` is a resource type NAME (see `GET /resources/types`); field keys are field names as returned by `GET /resources/fields?type={ref}` (the `name` key; field titles are accepted as a case-insensitive fallback). Type and field refs differ per server — always address by name. Unknown names return 400 with the offending name in the message (`UNKNOWN_TYPE` / `UNKNOWN_FIELD`). ### Values Field values are strings, numbers, booleans, or null (null clears the field). For list-type fields (dropdowns, checkboxes, category trees) pass the option NAMES — either comma-separated in one string or as a JSON array of strings. Options that don't exist are reported per-field in `fieldErrors` without failing the create. The resource is created under the linked user with the same archive state, usergroup scoping, and permission walls as an in-app upload. The title field participates in the same denormalised title handling as internal edits. ### Idempotency Pass an `Idempotency-Key` header (a unique random string per logical create, e.g. a UUID) to make retries safe. The first successful response with a given key is cached for 24 hours; replays return the same body byte-for-byte with `Idempotent-Replayed: true`. Reusing the key with a different request body returns 422 `IDEMPOTENCY_KEY_CONFLICT`.