List ledger subjects

Requires a workspace-bound API key with ledger:read. Lists the workspace's ledger subjects, newest opened first, each with its display label (the live preferred-label claim, if any) and the catalog entity it is anchored to. With entityId, returns the subjects anchored to that entity in one bounded page. An anchor is an index between the workspace ledger and the shared catalog; it is neither a claim nor a merge. Unsupported or repeated query parameters are rejected with HTTP 400.