v12.19 pass 9: clean up dead bindings flagged by the compiler

- set_pnl/consume_released_pnl: drop unused new_rel binding, replace
  with explicit underscored discard on the validation-only subtraction.
- enqueue_adl A-truncation: rename a_trunc_rem → _a_trunc_rem (the
  remainder is unused; we consume only a_candidate_u256).
- account_equity_trade_open_raw: idx arg is unused at present; name
  it _idx to silence the warning until either a caller uses it or
  we drop it from the signature.
- I256::checked_add_i256: the unsigned-overflow flags from the
  component overflowing_add calls are unused; the sign-based
  overflow detection below doesn't need them. Renamed to
  _overflow1/_overflow2.

Zero `warning: unused variable` in `cargo build --features test` now.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: aeyakovenko

src/percolator.rs

@@ -1749,7 +1749,9 @@ impl RiskEngine {
         if x > old_rel { return Err(RiskError::CorruptState); }
 
         let new_pos = old_pos.checked_sub(x).ok_or(RiskError::CorruptState)?;
-        let new_rel = old_rel.checked_sub(x).ok_or(RiskError::CorruptState)?;
+        // Validation-only subtraction; result unused (new_rel would equal
+        // old_rel - x >= 0 given the `x > old_rel` guard above).
+        let _ = old_rel.checked_sub(x).ok_or(RiskError::CorruptState)?;
         if new_pos < old_r { return Err(RiskError::CorruptState); }
 
         // Update pnl_pos_tot
@@ -2849,7 +2851,7 @@ impl RiskEngine {
         let a_old_u256 = U256::from_u128(a_old);
         let oi_post_u256 = U256::from_u128(oi_post);
         let oi_u256 = U256::from_u128(oi);
-        let (a_candidate_u256, a_trunc_rem) = mul_div_floor_u256_with_rem(
+        let (a_candidate_u256, _a_trunc_rem) = mul_div_floor_u256_with_rem(
             a_old_u256,
             oi_post_u256,
             oi_u256,
@@ -3277,7 +3279,7 @@ impl RiskEngine {
     /// `candidate_trade_pnl` is the signed execution-slippage PnL for this account
     /// from the candidate trade under evaluation.
     pub fn account_equity_trade_open_raw(
-        &self, account: &Account, idx: usize, candidate_trade_pnl: i128
+        &self, account: &Account, _idx: usize, candidate_trade_pnl: i128
     ) -> i128 {
         let trade_gain = if candidate_trade_pnl > 0 { candidate_trade_pnl as u128 } else { 0u128 };
 

src/wide_math.rs

@@ -870,8 +870,11 @@ impl I256 {
         let r_lo = rhs.lo_u128();
         let r_hi = rhs.hi_u128();
         let (lo, carry) = s_lo.overflowing_add(r_lo);
-        let (hi, overflow1) = s_hi.overflowing_add(r_hi);
-        let (hi, overflow2) = hi.overflowing_add(if carry { 1 } else { 0 });
+        // overflow bits unused — this is a wrapping-add for signed I256; the
+        // sign-based overflow detection below uses the result, not the
+        // unsigned-overflow flags.
+        let (hi, _overflow1) = s_hi.overflowing_add(r_hi);
+        let (hi, _overflow2) = hi.overflowing_add(if carry { 1 } else { 0 });
         let result = I256::from_lo_hi(lo, hi);
 
         let self_neg = self.is_negative();