Catalog #10 — upload the timestamped SIGNAL HISTORY that makes a webhook-driven strategy gradable.

Body: {"signals": [{"symbol": "NVDA", "ts": "2026-03-03T14:30:00Z"}, ...]} (<= 5000 rows). Stored ON the strategy (its spec carries signal_history), so any backtest of the strategy — POST /v1/backtests with strategy_id, or the per-alpha run — grades entries off it with the normal no-look-ahead discipline (signal ts → next-bar fill). Replaces any previous upload. Only meaningful on a webhook spec (entry.webhook: true) — refused in plain words otherwise. Owner-scoped (404 on someone else's id, indistinguishable from a missing one); audited.