fix: OptimizerV3 / OptimizerV3Push3 not explicitly typed against IOptimizer (#661)

- Optimizer: add `is IOptimizer` and mark getLiquidityParams() with
  `override`, making the interface conformance explicit at the base level.
  OptimizerV3 inherits it transitively via Optimizer.
- OptimizerV3Push3: add `is IOptimizer` and implement getLiquidityParams()
  that calls calculateParams() with zeroed inputs, returning bear-mode
  defaults (ci=0, anchorShare=0.3e18, anchorWidth=100, discoveryDepth=0.3e18).
  Behaviour is identical to the previous try/catch fallback used by
  LiquidityManager and the backtesting deployer.
- Update backtesting comments to reflect that getLiquidityParams() now
  exists on OptimizerV3Push3 (returns bear defaults via zeroed inputs).

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

onchain/script/backtesting/BacktestRunner.s.sol

@@ -134,8 +134,8 @@ contract BacktestRunner is Script {
         // ------------------------------------------------------------------
         // KrAIken system deployment (follows DeployLocal.sol pattern)
         //
-        // 1. Deploy OptimizerV3Push3 (no proxy — only exposes isBullMarket(),
-        //    causing LM to fall back to safe bear-mode defaults via try/catch).
+        // 1. Deploy OptimizerV3Push3 (no proxy — getLiquidityParams() uses zeroed
+        //    inputs, returning bear-mode defaults on every recenter).
         // 2. Deploy LiquidityManager pointing at the shadow pool.
         // 3. Wire BacktestKraiken.setLiquidityManager(lm).
         // 4. Set feeDestination = sender.