Full venue and metric catalog served to agents, each entry marked with the minimum plan that unlocks it. Returns an object, { venues, metrics, availableFrom }. Every metric lists the series intervals it is served at (1m, 5m, 1h, 1d; the plan decides which a key may use), and the metrics whose coarser values are rollups of minute values carry a one-sentence rollupNote. availableFrom["1m"] is when the first one-minute row was written (ISO 8601), or null before any. THE QUALITY BIT TABLE LIVES HERE: the qualityFlags entry in metrics carries the whole 16-bit taxonomy inline as bits — bit index, mask, name, description, the metric families each bit calls into question, and whether anything currently sets it. This API is the SERVER of that taxonomy; fetch it, never re-declare it. There is deliberately no second route serving the same table.