malkhut(docs): updated all docs — fee model, markout, urgency threshold

MALKHUT/docs/OB_MICROSTRUCTURE_STUDY.md

@@ -405,6 +405,16 @@ if the market moves adversely after execution. The system scores fills by markou
 
 **Generalizable:** score fills by post-fill markout. Model fill-CONDITIONAL-on-adverse-flow.
 
+### Fee Model (BingX, No Rebates)
+
+BingX reports fees as NEGATIVE. MALKHUT convention: positive = cost.
+- Maker fee: 2.0 bps (you pay)
+- Taker fee: 5.0 bps (you pay)
+- Fee savings: 3.0 bps (maker saves 3bp vs taker)
+- There are NO rebates on BingX.
+
+The system learns: prefer maker when fee savings > fill probability cost.
+
 ### Fill = Queue × Flow Intensity
 
 Fill probability is driven by **trade-arrival intensity** (the tape), not the static book.