CLAUDE: TEMP probe — print gpu_clt_ref stats after first ref convert (JNA)

Diagnostic for the CORR2D-all-NaN numeric divergence: after the first
ref_scene=true convert, read back gpu_clt_ref (tp_proc_get_clt use_ref=1) and
print NaN%/nonzero/min/max once. Confirms whether the reference convert
populates gpu_clt_ref at all (vs scene gpu_clt which is correct -> SOURCE).

Prints one "PROBE gpu_clt_ref[cam0]: ..." line to System.out (captured in the
per-scene -SYSTEM_OUT.log). TEMP — remove after the divergence is fixed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/main/java/com/elphel/imagej/gpu/jna/GpuQuadJna.java

@@ -249,11 +249,26 @@ public class GpuQuadJna extends GpuQuad {
     }
 
     // ---- direct CLT conversion (+ the fragile no_kernels / use_center_image / erase_clt / ref_scene paths) ----
+    // TEMP PROBE flag (By Claude 06/26/2026): print gpu_clt_ref stats once after the first ref_scene convert,
+    // to confirm whether the reference convert actually populates gpu_clt_ref (CORR2D-all-NaN divergence).
+    // REMOVE after the reference-CLT divergence is fixed.
+    private boolean clt_ref_probed = false;
     @Override public void execConvertDirect(boolean ref_scene, int[] wh, int erase_clt, boolean no_kernels, boolean use_center_image) {
         boolean skip_kernels = rectilinear || no_kernels;
         if (!skip_kernels) setConvolutionKernels(false);
         if (!rectilinear)  setBayerImages(false, use_center_image);
         lib.tp_proc_exec_convert_direct(proc, ref_scene ? 1 : 0, erase_clt, no_kernels ? 1 : 0);
+        if (ref_scene && !clt_ref_probed) { // TEMP PROBE — remove after fix
+            clt_ref_probed = true;
+            int sz = getCltSize(true);
+            float[] clt = new float[sz];
+            lib.tp_proc_get_clt(proc, 0, 1, clt);
+            int nan = 0, nz = 0; float mn = Float.POSITIVE_INFINITY, mx = Float.NEGATIVE_INFINITY;
+            for (float v : clt) { if (Float.isNaN(v)) nan++; else { if (v != 0f) nz++; if (v < mn) mn = v; if (v > mx) mx = v; } }
+            System.out.println(String.format(
+                "PROBE gpu_clt_ref[cam0]: size=%d NaN=%.1f%% nonzero=%d finite[min=%g max=%g] (erase_clt=%d)",
+                sz, 100.0 * nan / Math.max(sz, 1), nz, (nz > 0 ? mn : 0f), (nz > 0 ? mx : 0f), erase_clt));
+        }
     }
 
     // ---- inverse CLT -> RBG ----