Panel layout stage 3: per-panel spot finding (CPU+GPU, CCL) and raster algorithms on the plane raster

Spot finding works panel by panel, as the FPGA path does per JUNGFRAU module. PanelBoxes (common/) gives
one box per DetectorModule; an empty table gives one box, the whole image, so every clamp reduces to the
old image bounds in the same evaluation order (rotation sets, EIGER, CCDs, our JUNGFRAU unchanged).
- ImageSpotFinder::SetPanels: the CPU local-box pass (dense, count-threshold and the DetectAt/candidate
  path of the adaptive finder) slides its windows inside each panel box; host CCL labels panel by panel;
  pixels on no panel are folded into the resolution mask.
- GPU: analyze_pixel tiles each panel (warps numbered panel after panel), analyze_candidates and
  union_neighbours clip to the pixel's panel, the device spot carries its panel; the GPU list is put in
  panel order so it equals the host's.
- DiffractionSpot carries its panel; SpotAnalyze maps by ImageToPlane(panel, ...) (d_A on the plane).
- ImagePreprocessorBuffer::GatherTiles (CPU+GPU) clips each square to the panel of its centre.
- MXAnalysisWithoutFPGA and the pre-scan workers hand the module table to finders and buffers.

Raster algorithms: new common/AssembleToPlane.h (PlaneRasterOf, AssembleToPlane nearest-pixel gather with
gaps, GatherFromPlane back to stored pixels; empty table = copy). With panels, ShadowFinder::GetMask runs on
the projection assembled to the plane raster and gathers the mask back per stored pixel (CPU route);
FindBeamCenterFFT scores the assembled projection and reports plane coordinates; the detector diagnostic
JPEG shows the assembled plane. Without panels all three take their old path.

Harness: PanelLayout_SpotsNeverCrossPanels enabled (count threshold and SNR on the edge scene), new
PanelLayout_SpotFinderParity (CPU vs GPU, local box and adaptive, on the stacked layout),
PanelLayout_AssembleToPlane, PanelLayout_ShadowFinder, PanelLayout_BeamCenterFFT,
PanelLayout_DetectorDiagnostic (stacked vs assembled image cut to the raster).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CeEGgpKdfkCTJb3YNMJcu

common/DiffractionSpot.cpp

@@ -24,8 +24,9 @@ DiffractionSpot& DiffractionSpot::operator+=(const DiffractionSpot &other) {
 }
 
 DiffractionSpot::DiffractionSpot(int64_t x_sum, int64_t y_sum, int64_t in_pixel_count,
-                                 int64_t in_photons, int64_t in_max_photons)
-    : x(x_sum), y(y_sum), pixel_count(in_pixel_count), photons(in_photons), max_photons(in_max_photons) {}
+                                 int64_t in_photons, int64_t in_max_photons, int64_t in_panel)
+    : x(x_sum), y(y_sum), pixel_count(in_pixel_count), photons(in_photons), max_photons(in_max_photons),
+      panel(in_panel) {}
 
 int64_t DiffractionSpot::Count() const {
     return photons;
@@ -44,6 +45,14 @@ Coord DiffractionSpot::RawCoord() const {
             static_cast<float>(static_cast<double>(y) / static_cast<double>(photons)), 0};
 }
 
+int64_t DiffractionSpot::Panel() const {
+    return panel;
+}
+
+void DiffractionSpot::Panel(int64_t in_panel) {
+    panel = in_panel;
+}
+
 int64_t DiffractionSpot::PixelCount() const {
     return pixel_count;
 }