fix: address PR #168 review findings in OptimizerV3Push3

- Add `require(averageTaxRate <= 1e18, "Invalid tax rate")` to match
  the existing `percentageStaked` guard and prevent silent acceptance
  of out-of-range values.
- Expand contract-level NatSpec with a @dev note clarifying this is an
  equivalence proof only: it intentionally exposes `isBullMarket` alone
  and is not a deployable upgrade (full optimizer interface missing).

All 15 Foundry tests pass (15 unit + fuzz).

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

onchain/src/OptimizerV3Push3.sol

@@ -5,6 +5,10 @@ pragma solidity ^0.8.19;
  * @title OptimizerV3Push3
  * @notice Auto-generated from optimizer_v3.push3 via Push3→Solidity transpiler.
  *         Implements the same isBullMarket logic as OptimizerV3.
+ * @dev    This contract is an equivalence proof, not a deployable upgrade.
+ *         It intentionally exposes only `isBullMarket` and does NOT implement
+ *         the full optimizer interface (e.g. `getLiquidityParams`).  Wiring it
+ *         into the proxy upgrade path would require completing that interface first.
  */
 contract OptimizerV3Push3 {
     /**
@@ -18,6 +22,7 @@ contract OptimizerV3Push3 {
         uint256 averageTaxRate
     ) public pure returns (bool bull) {
         require(percentageStaked <= 1e18, "Invalid percentage staked");
+        require(averageTaxRate <= 1e18, "Invalid tax rate");
         uint256 taxrate = uint256(averageTaxRate);
         uint256 staked = uint256(((percentageStaked * 100) / 1000000000000000000));
         bool b33;