Delete a workspace secret

Deletes a secret from the workspace of the authenticated API key. Returns 204 with no body on success and 404 when the secret does not exist in the selected scope. Writes return 503 while vault writes are disabled for the caller. The scope is selected by the API key: workspace routes act on the key's active workspace and intern routes act on one intern inside that workspace. There is no default workspace and no fallback to another scope. Every vault route, including reads, requires access to the Intern API programme and returns 404 outside it. Requests on regional hostnames such as eu.openrouter.ai are refused. API key required.