Add LAZ integrity check to skip corrupted files early

Validate file readability before PDAL classification. Corrupted/truncated
files are detected instantly via laspy header read and skipped with a clear
error message pointing to re-download, instead of wasting time on PDAL
and repair attempts that will fail anyway.

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

lidar_pipeline/pipeline.py

@@ -272,6 +272,11 @@ class LidarArchaeoPipeline:
         logger.info(f"FICHIER : {basename}")
         logger.info("=" * 60)
 
+        # Validate file integrity before any processing
+        from .dtm import validate_laz
+        if not validate_laz(laz_file):
+            return False
+
         # Skip ground classification + DTM if DTM already exists with matching resolution
         # --force only affects visualizations/PDF, not classification/DTM
         # Use --force-classification to force reclassification