List Agents

List the agent namespaces this developer has written under (the distinct non-null agent_id values), each with its active memory + fact counts and last-active time, plus cap, the most agent names a write may bring in (0 when nothing caps them, as on an install of one's own), and used, how many of them the cap counts.

The namespace set counts memories AND direct fact writes, including soft-deleted / invalidated rows; the per-agent memories/facts counts reflect only active items, so an agent whose data was all forgotten still appears, with zero counts, until DELETE /v1/agents/{agent_id} purges it. The default (null) namespace is never counted, and omitted.