Mirrors GET /api/v1/topologies/{id}/events: subscribes to identity.>
on the bus for the duration of the request and forwards each event as
a named SSE frame (formed / observation.linked / merged / unmerged).
The endpoint is broadly scoped (every identity event, not per-uuid)
because both AttackerDetail and IdentityDetail need the same
firehose: AttackerDetail watches for an identity.formed that finally
binds its identity_id; IdentityDetail watches for
observation.linked / merged / unmerged against its current row. A
per-uuid filter would force the client to know its identity before
subscribing, which it doesn't always.
JWT via ?token= (EventSource can't set headers), require_stream_viewer
gate, sse_connection_slot per-user cap, snapshot-on-connect with
the first 50 identities so the client buffer renders without a
separate REST call.
Bus-disabled / unreachable path keeps the connection alive on
keepalives so the client doesn't reconnect-storm; it can re-poll
the REST API on its own timer.