Naming an engine an install had not enabled was a 400, and there was no way to
find out beforehand — the client had to know, or guess and handle the refusal.

GET /v1/ocr/engines answers it from this install's own config: every engine
with `enabled` and, when it is not, a `reason` that names the setting to
change (an unaccepted licence is reported as such rather than as merely
disabled, because that is a different checkbox). Each row also carries `kind`
— an engine owns its weights, a pipeline drives a model — the `aliases` that
also resolve to it, and `returns`, so a caller that needs coordinates can see
that olmOCR has none rather than discovering it in an empty field. The top
level reports both what the operator wrote as the default and what it resolves
to.

Where the model runs is deliberately not in the answer. It is configuration,
it can differ between two requests, and a client that could see it would start
depending on it. A test asserts the payload mentions no pod, node or address.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PxYHWbCAjjjD7A1rhFKtaW