chore: update .gitignore, CLAUDE.md, training_log.json, and ml_filter.py

- Added .worktrees/ to .gitignore to prevent tracking of worktree files.
- Marked `optuna-precision-objective-plan` as completed in CLAUDE.md.
- Added new training log entry for a LightGBM model with updated parameters and performance metrics in training_log.json.
- Updated error handling in ml_filter.py to return False on prediction errors instead of True, improving the robustness of the ML filter.

models/training_log.json

@@ -476,5 +476,30 @@
       "reg_lambda": 0.082872
     },
     "weight_scale": 1.431662
+  },
+  {
+    "date": "2026-03-05T02:00:24.489871",
+    "backend": "lgbm",
+    "auc": 0.9448,
+    "best_threshold": 0.3075,
+    "best_precision": 0.452,
+    "best_recall": 0.463,
+    "samples": 3246,
+    "features": 26,
+    "time_weight_decay": 2.0,
+    "model_path": "models/lgbm_filter.pkl",
+    "tuned_params_path": null,
+    "lgbm_params": {
+      "n_estimators": 221,
+      "learning_rate": 0.031072,
+      "max_depth": 5,
+      "num_leaves": 20,
+      "min_child_samples": 39,
+      "subsample": 0.83244,
+      "colsample_bytree": 0.526349,
+      "reg_alpha": 0.062177,
+      "reg_lambda": 0.082872
+    },
+    "weight_scale": 1.431662
   }
 ]