Retrieve Y2 Global Knowledge

Searches shared Y2 knowledge and, when requested, the key's workspace knowledge. Y2 determines access from the key. The request cannot supply a user or workspace ID. Results include source IDs and citations. They omit provider and access-control attributes. This operation requires a workspace-bound API key with `intel:knowledge`. It does not support x402. Agent Y2 keys continue to use `agent:y2`. The agent may invoke this retrieval tool internally when the workspace is entitled to Chat.