Vest: a crypto leg's stop holds back the engine's default slippage, not NDX's

Crypto (exchangeInfo asset "crypto": BTC, ETH, SOL, HYPE) trades on weekends
when NDX, SPX and GC are shut, but its stop slippage on Vest is unmeasured, and
its book is a fraction of NDX's: about $10M an hour on a weekend against $600M,
with a batch's stops firing together. Its stops now leave 0.1% of the
position unspent (the engine's default) instead of the 0.02% measured on NDX
stop-outs; every other symbol keeps 0.02%.

The share rides on the picked contract and is used wherever a Vest leg's stop
is sized: the batch's plan, the leg's own stop, the dashboard's next stop, and
the 7:55 PM ET reset guard, which now sums each open position's own share.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/platform-client.ts

@@ -53,6 +53,10 @@ export interface PlatformContract {
      *  says: no leg starts that wouldn't be done by then (clearsClose), each
      *  account's at its own size (fireLeg). */
     closesAt?: number;
+    /** This instrument's share of notional a stop may fill past its price,
+     *  where it differs from the client's stopSlippageFraction (Vest: crypto,
+     *  unmeasured, keeps the engine's default). */
+    stopSlippageFraction?: number;
 }
 
 /** What an order is for, where the caller knows (see sendOrder). */