Delete a deployed bot that NEVER traded. A bot that traded is RETIRED.

SESSION-OWNER ONLY, mirroring /approve: destroying a bot is a human act, so an account key PAIR (the agent credential) can never do it — a pair-only caller gets 401 from require_session_user. ?confirm=true is REQUIRED (400 otherwise). 404 "Deployment not found" for a desk that isn't the caller's or a bot that isn't on it — byte-identical to a bot that never existed.

THE HONEST-MONEY RULE. Hard delete is allowed ONLY when the deployment has ZERO position history AND ZERO order history (db.deployment_history_counts: positions open or closed, and the orders tied to them). If either ever existed the answer is 409 and the bot can only be RETIRED — the money ledger has to stay auditable, and retiring keeps every trade on the record.

OPEN POSITIONS CANNOT BE ORPHANED, by construction: an open position IS position history, so such a bot is refused here and retired instead. What RETIRE actually does to an open position (verified in paper_sim, 2026-07-29; settlement clause added 2026-08-19 — do not soften either half): the strategy's own exit rule NEVER runs again on that position. No stop-loss, no take-profit, no ratchet, no rule/hold exit, no time-stop or flatten, no desk stop. The position stays status='open' and honest — it is still re-marked (both by the walk and by every positions read, since paper_manual.positions_view marks every open row on the desk regardless of which bot opened it) and any protective order already resting on it still fills from the desk matcher — but nothing will close it on the strategy's terms. Closing it is the member's move (the manual close on the desk).

THE ONE EXIT THAT STILL RUNS IS THE MARKET'S OWN: contract-mandated SETTLEMENT — an option at expiry, a credit/covered structure at its expiry, an equity that delists. That is not the strategy trading; the contract ended on its own. Without it a retired bot's expired contract could be closed by NOBODY: the walk skipped it and a dead contract has no live quote, so the manual close refuses it too (NoLiveQuote). Measured on the live desk — position 4416, an AMZN call that expired 2026-08-17 on a bot retired 2026-08-03. So a retired bot now walks exactly the SHELF path: mark, never trade, settle what the market has already ended.

A retired bot's open position is MARKED and STILL TRADEABLE BY HAND; it is not auto-managed by the strategy.

A zero-history delete cascades vega_deployment_transitions then the deployment row (one transaction). Returns {"deleted": deploy_id, "cascade": {...}}.