Fix corrupted COPC detection, add CSF→SMRF fallback, improve MSRM colormap, add SVF and anisotropic openness

- validate_laz: verify point data accessibility (not just headers) to detect
  corrupted COPC files that pass header checks but fail on data reads
- classify_ground: fallback from CSF to SMRF when CSF produces no ground
  points or PDAL errors (fixes 2/9 failing tiles)
- MSRM: preserve sign in weighted combination so RdBu_r colormap shows
  both red (elevated) and blue (depressed) instead of red only
- Add Sky-View Factor (SVF) visualization: cos²(horizon angle) over 16
  directions, excellent for archaeological earthwork detection
- Add Anisotropic Openness: directional weighting (NW-SE/NE-SW) enhances
  linear feature detection aligned with common settlement patterns
- Remove anomalies and flow visualizations (replaced by SVF + aniso_open)
- Location inset: use IGN topographic map at zoom 10 instead of simplified
  France outline, with red rectangle marker and fallback
- Remove flow (hydrological accumulation) from VIZ_STEPS

lidar_pipeline/pipeline.py

@@ -60,8 +60,8 @@ from .visualizations import (
     generate_hillshade, generate_slope, generate_aspect, generate_curvature,
     generate_lrm, generate_openness,
     generate_mslrm, generate_tpi, generate_sailore,
-    generate_roughness, generate_anomalies, generate_wavelet,
-    generate_flow,
+    generate_roughness, generate_wavelet,
+    generate_svf, generate_aniso_open,
 )
 from .gpu import gpu_cleanup
 from .ign import generate_ign_overlay
@@ -83,9 +83,9 @@ VIZ_STEPS = [
     ('tpi',        generate_tpi),
     ('sailore',    generate_sailore),
     ('roughness',  generate_roughness),
-    ('anomalies',  generate_anomalies),
+    ('svf',        generate_svf),
+    ('aniso_open', generate_aniso_open),
     ('wavelet',    generate_wavelet),
-    ('flow',       generate_flow),
     ('ortho',      lambda d, b, v, r: generate_ign_overlay(
                     d, b, v, r,
                     layer='ORTHOIMAGERY.ORTHOPHOTOS',