Use option (BTC) index for coin-to-U; never fall back to ETH perp mark. Also add no-server-ops Cursor rule. Co-authored-by: Cursor <cursoragent@cursor.com>
Lock one mode per instance/subaccount, cross-asset BTC option/ETH perp sizing, combo-U exit, and ship docs/tests/audit. Co-authored-by: Cursor <cursoragent@cursor.com>