List tagged emergent signals

Lists cached Y2 emergent SIGINT signals with ontology-aligned subjects, normalized subject keys, tags, source-report metadata, timestamps, and available geographic, observation, or entity links. Required scopes vary by `domain` filter: - `domain=cyber` or `domain=technology` -> `intel:cyber` or `intel:explorer` - `domain=markets` or `domain=supply_chain` -> `intel:finint` or `intel:explorer` - other domain filters -> `intel:explorer` - no `domain` filter -> any of `intel:cyber`, `intel:finint`, or `intel:explorer` Public x402 callers receive global and community signals. Authenticated API-key callers also receive authorized workspace and private rows.