PINK: fix fee-sign bug + WARN-unfreeze — 451/451 tests green

Defect A (fee sign): bingx_user_stream._normalise_order flipped to
  fee = -raw_fee so BingX negative-n costs arrive as positive kernel
  costs.  k_maker_rebates no longer accumulates phantom rebates.

Defect B (opening fee dropped): fill_qty now falls back to "z"
  (cumFilledQty) when "l" (lastFilledQty) is zero/absent, so
  apply_predicted_fill computes a non-zero opening-leg fee.

Architectural fix (WARN unfreezes): lib.rs reconcile() now unfreezes
  capital_frozen on WARN as well as OK.  WARN (0.01-20 USDT delta) is
  normal in-flight settlement — only ERROR (≥20, unexplained) should
  halt ENTERs.  The old keep-state logic trapped the kernel permanently
  frozen after the first trade's ENTER predicted-fee phase pushed delta
  briefly into ERROR.

Acceptance criterion: |k_capital - bingx_balance| < 1 USDT, frozen=False
after every round-trip trade — verified numerically against T-1/T-2
ground truth from the CRITICAL doc.

Docs: CRITICAL_AGENT-TODO_ACCOUNTING_BUGFIX.md §12-13 (fix record),
      CAPITAL_BOOKKEEPING_DESIGN.md §8 (kernel spec), SYSTEM_BIBLE §11.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

prod/clean_arch/dita_v2/bingx_user_stream.py

@@ -333,15 +333,22 @@ class BingxUserStream:
             str(o.get("o") or o.get("type") or "MARKET").upper() == "LIMIT"
             and status in {"FILLED", "PARTIALLY_FILLED"}
         ))
-        # Fees: BingX sends commission as positive for costs, negative for rebates
+        # DEFECT A FIX: BingX sends "n" (commission) NEGATIVE for costs, POSITIVE for
+        # rebates on VST.  Kernel convention is the opposite: POSITIVE = cost, NEGATIVE
+        # = rebate.  Flip at this boundary so the kernel never sees wrong-sign fees.
         raw_fee = _safe_float(o.get("n") or 0.0)
-        fee = raw_fee  # may be negative (rebate)
+        fee = -raw_fee  # BingX cost (negative n) → kernel cost (positive fee)
+        # DEFECT B FIX: prefer "l" (lastFilledQty) when non-zero; fall back to "z"
+        # (cumFilledQty) for ENTER fills where BingX reports qty only in "z".
+        _last_qty = _safe_float(o.get("l") or 0.0)
+        _cum_qty  = _safe_float(o.get("z") or o.get("cumFilledQty") or 0.0)
+        fill_qty  = _last_qty if _last_qty > 0.0 else _cum_qty
         return ExchangeEvent(
             kind=kind,
             event_id=str(o.get("i") or o.get("orderId") or uuid.uuid4().hex),
             exchange_ts=ts,
             fill_price=_safe_float(o.get("L") or o.get("ap") or o.get("p")),
-            fill_qty=_safe_float(o.get("l") or o.get("lastFilledQty") or 0.0),
+            fill_qty=fill_qty,
             fee=fee,
             fee_asset=str(o.get("N") or ""),
             realized_pnl=_safe_float(o.get("rp") or o.get("realizedPnl") or 0.0),