Add persistent trial history DB (append-only, survives --clean)

- history.db: SQLite append-only, never deleted by --clean
- history.csv: Auto-exported after each trial (live updates)
- Logs: DVs, results, feasibility, status, solve time, iter path
- Cross-study queries: full lineage across all runs/phases
- --clean only resets Optuna DB, history preserved

projects/hydrotech-beam/studies/01_doe_landscape/run_doe.py

@@ -41,6 +41,7 @@ from geometric_checks import (
     FeasibilityResult,
     check_feasibility,
 )
+from history import TrialHistory
 from nx_interface import TrialInput, TrialResult, create_solver
 from sampling import DV_DEFINITIONS, generate_lhs_samples, points_to_dicts
 
@@ -103,12 +104,16 @@ def constraints_func(trial: optuna.trial.FrozenTrial) -> list[float]:
 def evaluate_trial(
     trial: optuna.Trial,
     solver: Any,
+    history: TrialHistory | None = None,
+    study_name: str = "",
 ) -> float:
     """Evaluate a single trial: geometric check → NX solve → extract.
 
     Args:
         trial: Optuna trial (with parameters already suggested/enqueued).
         solver: NX solver instance (stub or real).
+        history: Persistent trial history logger (append-only).
+        study_name: Study name for history logging.
 
     Returns:
         Objective value (mass in kg). Returns INFEASIBLE_MASS for
@@ -152,6 +157,13 @@ def evaluate_trial(
     trial.set_user_attr("ligament", geo_result.ligament)
     trial.set_user_attr("web_clearance", geo_result.web_clearance)
 
+    params = {
+        "beam_half_core_thickness": dv1,
+        "beam_face_thickness": dv2,
+        "holes_diameter": dv3,
+        "hole_count": dv4,
+    }
+
     if not geo_result.feasible:
         logger.warning(
             "Trial %d: GEOMETRICALLY INFEASIBLE — %s",
@@ -162,6 +174,13 @@ def evaluate_trial(
         trial.set_user_attr("tip_displacement", INFEASIBLE_DISPLACEMENT)
         trial.set_user_attr("max_von_mises", INFEASIBLE_STRESS)
         trial.set_user_attr("mass", INFEASIBLE_MASS)
+        if history:
+            history.log_trial(
+                study_name=study_name, trial_id=trial_num, params=params,
+                geo_feasible=False, status="GEO_INFEASIBLE",
+                error_message=geo_result.reason,
+                iteration_number=trial_num + 1,
+            )
         return INFEASIBLE_MASS
 
     # NX evaluation
@@ -188,6 +207,14 @@ def evaluate_trial(
         trial.set_user_attr("tip_displacement", INFEASIBLE_DISPLACEMENT)
         trial.set_user_attr("max_von_mises", INFEASIBLE_STRESS)
         trial.set_user_attr("mass", INFEASIBLE_MASS)
+        if history:
+            history.log_trial(
+                study_name=study_name, trial_id=trial_num, params=params,
+                status="FAILED", error_message=nx_result.error_message,
+                solve_time_s=round(t_elapsed, 2),
+                iter_path=nx_result.iteration_dir,
+                iteration_number=trial_num + 1,
+            )
         return INFEASIBLE_MASS
 
     # Record successful results
@@ -214,6 +241,20 @@ def evaluate_trial(
         t_elapsed,
     )
 
+    if history:
+        history.log_trial(
+            study_name=study_name, trial_id=trial_num, params=params,
+            mass_kg=nx_result.mass,
+            tip_displacement_mm=nx_result.tip_displacement,
+            max_von_mises_mpa=nx_result.max_von_mises,
+            geo_feasible=True,
+            status="COMPLETE",
+            solve_time_s=round(t_elapsed, 2),
+            iter_path=nx_result.iteration_dir,
+            iteration_number=trial_num + 1,
+        )
+        history.export_csv()  # Live update CSV after each trial
+
     return nx_result.mass
 
 
@@ -419,7 +460,7 @@ def run_study(args: argparse.Namespace) -> None:
     storage = f"sqlite:///{db_path}"
 
     if args.clean and db_path.exists():
-        logger.info("--clean flag: deleting existing DB at %s", db_path)
+        logger.info("--clean flag: deleting Optuna DB at %s (history.db preserved)", db_path)
         db_path.unlink()
 
     if args.resume:
@@ -449,13 +490,17 @@ def run_study(args: argparse.Namespace) -> None:
         logger.info("Enqueued %d trials (1 baseline + %d LHS)", n_trials, n_trials - 1)
 
     # -----------------------------------------------------------------------
-    # 3. Create solver
+    # 3. Create solver + history
     # -----------------------------------------------------------------------
     solver = create_solver(
         backend=args.backend,
         model_dir=args.model_dir,
     )
 
+    # Persistent history — NEVER deleted by --clean
+    history = TrialHistory(results_dir)
+    study_name = args.study_name
+
     # -----------------------------------------------------------------------
     # 4. Run all trials
     # -----------------------------------------------------------------------
@@ -469,7 +514,7 @@ def run_study(args: argparse.Namespace) -> None:
     optuna.logging.set_verbosity(optuna.logging.WARNING)
 
     study.optimize(
-        lambda trial: evaluate_trial(trial, solver),
+        lambda trial: evaluate_trial(trial, solver, history, study_name),
         n_trials=n_trials,
         callbacks=[_progress_callback],
     )
@@ -497,6 +542,11 @@ def run_study(args: argparse.Namespace) -> None:
     # Cleanup
     solver.close()
 
+    # Final history export + summary
+    history.close()
+    hist_summary = history.get_study_summary(study_name)
+    logger.info("History DB: %d total records across all studies", hist_summary["total"])
+
 
 def _progress_callback(study: optuna.Study, trial: optuna.trial.FrozenTrial) -> None:
     """Log progress after each trial."""