Fix: SQLite duplicate study (load_if_exists), sampling crash with n<11, add --clean flag

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

@@ -173,6 +173,16 @@ def _ensure_integer_coverage(
         logger.info("All 11 hole_count levels represented ✓")
         return samples
 
+    # Skip patching when sample size is too small to cover all levels
+    n_samples = len(samples)
+    if n_samples < len(all_levels):
+        logger.info(
+            "Only %d samples — too few to cover all 11 hole_count levels "
+            "(need ≥11). Skipping stratified patching.",
+            n_samples,
+        )
+        return samples
+
     logger.warning(
         "Missing hole_count levels: %s — patching with replacements",
         sorted(missing_levels),