List engrams the selected model can run

Which engine reads the memory (see GET /api/v1/models). All live models share one memory per workspace, so you can store with one and recall with another. A retired model answers 410 with error.type gone_error and error.code 0, except on DELETE /api/v1/memory/collection, which deletes the store under any model. Until then, a model scheduled to retire names the day in a Sunset header (RFC 8594) on every answer it serves, the same date GET /api/v1/models lists as retires_at.