CLAUDE: Dual-pass nadir rendering (original + rectilinear)

Update calling code in OpticalFlow.java to compute nadir_pXpYD once and
render two passes when either nadir_gen or nadir_undistort is enabled:
- nadir_gen=true  → renderNadirSequence(..., false) → *-NADIR-MERGED
- nadir_undistort=true → renderNadirSequence(..., true)  → *-NADIR-MERGED-RECTILINEAR

The nadir_pXpYD array is deep-copied per scene for the undistort pass so
the original sensor-coordinate data is preserved for the non-undistorted pass.
Co-authored-by: Claude <claude@elphel.com>

src/main/java/com/elphel/imagej/tileprocessor/OpticalFlow.java

@@ -8049,18 +8049,21 @@ java.lang.NullPointerException
 								null,               // "GPU-SHIFTED-D"+clt_parameters.disparity, // String      suffix,
 								imp_terrain_disp);       // imp_scenes); // ImagePlus   imp)
 						// Nadir per-scene rendering for OpenMVS/COLMAP input
-						if (clt_parameters.imp.nadir_gen) {
+						if (clt_parameters.imp.nadir_gen || clt_parameters.imp.nadir_undistort) {
 							double [][][] nadir_pXpYD = getNadirDisparityMaps(
 									clt_parameters,    // CLTParameters clt_parameters,
 									terrain_disparity, // double []     terrain_disparity,
 									quadCLTs,          // QuadCLT []    quadCLTs,
 									master_CLT,        // QuadCLT       ref_scene,
 									debugLevel);       // int           debugLevel
+							if (nadir_pXpYD != null) {
+								if (clt_parameters.imp.nadir_gen) {
 									ImagePlus imp_nadir = renderNadirSequence(
 											clt_parameters,    // CLTParameters clt_parameters,
 											nadir_pXpYD,       // double [][][] nadir_pXpYD,
 											quadCLTs,          // QuadCLT []    quadCLTs,
 											master_CLT,        // QuadCLT       ref_scene,
+											false,             // boolean       undistort,
 											debugLevel);       // int           debugLevel
 									if (imp_nadir != null) {
 										master_CLT.saveImagePlusInModelDirectory(
@@ -8068,6 +8071,22 @@ java.lang.NullPointerException
 												imp_nadir);  // ImagePlus imp
 									}
 								}
+								if (clt_parameters.imp.nadir_undistort) {
+									ImagePlus imp_nadir_rect = renderNadirSequence(
+											clt_parameters,    // CLTParameters clt_parameters,
+											nadir_pXpYD,       // double [][][] nadir_pXpYD,
+											quadCLTs,          // QuadCLT []    quadCLTs,
+											master_CLT,        // QuadCLT       ref_scene,
+											true,              // boolean       undistort,
+											debugLevel);       // int           debugLevel
+									if (imp_nadir_rect != null) {
+										master_CLT.saveImagePlusInModelDirectory(
+												null,            // String    suffix,
+												imp_nadir_rect); // ImagePlus imp
+									}
+								}
+							}
+						}
 					}
 				}
 			}
@@ -10932,13 +10951,15 @@ java.lang.NullPointerException
     		double [][][]  nadir_pXpYD,
     		QuadCLT []     quadCLTs,
     		QuadCLT        ref_scene,
+    		boolean        undistort,
     		int            debugLevel) {
     	QuadCLT[] selected_scenes = selectScenes(quadCLTs, ref_scene);
     	if (selected_scenes.length == 0) return null;
     	ErsCorrection ers_reference = ref_scene.getErsCorrection();
     	boolean merge_all = true;   // always produce single-channel merged output
     	boolean toRGB     = false;
-    	String  suffix    = ref_scene.getImageName() + "-NADIR-MERGED";
+    	String  suffix    = ref_scene.getImageName()
+    			+ (undistort ? "-NADIR-MERGED-RECTILINEAR" : "-NADIR-MERGED");
     	ImageStack stack_scenes = null;
     	for (int nscene = 0; nscene < selected_scenes.length; nscene++) {
     		if (nadir_pXpYD[nscene] == null) continue;
@@ -10951,9 +10972,17 @@ java.lang.NullPointerException
     					scene_ers_xyz_dt, // double [] ers_xyz_dt
     					scene_ers_atr_dt);// double [] ers_atr_dt
     		}
-    		// Optionally undistort pX,pY so rendered images are rectilinear (COLMAP PINHOLE-compatible)
-    		if (clt_parameters.imp.nadir_undistort) {
-    			undistortPxPy(nadir_pXpYD[nscene], selected_scenes[nscene].getErsCorrection());
+    		// Select tile array: use a shallow-cloned copy when undistorting so the
+    		// original nadir_pXpYD is preserved for a potential second (non-undistorted) pass.
+    		double[][] pXpYD_scene;
+    		if (undistort) {
+    			pXpYD_scene = nadir_pXpYD[nscene].clone(); // shallow: tile refs copied
+    			for (int t = 0; t < pXpYD_scene.length; t++) {
+    				if (pXpYD_scene[t] != null) pXpYD_scene[t] = pXpYD_scene[t].clone();
+    			}
+    			undistortPxPy(pXpYD_scene, selected_scenes[nscene].getErsCorrection());
+    		} else {
+    			pXpYD_scene = nadir_pXpYD[nscene];
     		}
     		// Render from scene's own position: ZERO3 offset, scene is its own reference
     		ImagePlus imp_scene = QuadCLT.renderGPUFromDSI(
@@ -10962,7 +10991,7 @@ java.lang.NullPointerException
     				null,                             // final Rectangle full_woi_in
     				clt_parameters,                   // CLTParameters   clt_parameters
     				null,                             // double []       disparity_ref (use pXpYD)
-    				nadir_pXpYD[nscene],              // double [][]     ref_pXpYD
+    				pXpYD_scene,                      // double [][]     ref_pXpYD
     				ZERO3,                            // final double [] scene_xyz (own frame)
     				ZERO3,                            // final double [] scene_atr (own frame)
     				selected_scenes[nscene],          // final QuadCLT   scene