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

image_analysis/image_preprocessing/ImagePreprocessorBuffer.h

@@ -8,8 +8,15 @@
 #include <cstddef>
 #include <climits>
 
+#include "../../common/PanelBoxes.h"
+
 class ImagePreprocessorBuffer {
 protected:
+    // The panels the image is made of (PanelBoxes); empty means one, the whole image.
+    std::vector<PanelBox> panels;
+    // The box the square about pixel (x, y) is clipped to: its panel's, or the image's.
+    PanelBox TileBox(int32_t x, int32_t y, int width) const;
+
     // The image size, kept apart from `buffer` so size() still answers when the host copy was not
     // allocated at all (see the host_mirror constructor).
     const size_t npixels;
@@ -46,9 +53,13 @@ public:
     virtual void Gather(const std::vector<uint32_t> &npixel, std::vector<int32_t> &values) const;
 
     // The (2*half+1)^2 pixels about each (x[i], y[i]) of the image, `width` pixels wide: square after
-    // square, each row by row, with a pixel off the image read as INT32_MIN. Valid until the next call.
+    // square, each row by row, with a pixel off the image - or off the panel (x[i], y[i]) is on - read as
+    // INT32_MIN. Valid until the next call.
     virtual const int32_t *GatherTiles(const std::vector<int32_t> &x, const std::vector<int32_t> &y,
                                        int width, int half);
+    // The panels of the image, for GatherTiles. Default: none, the whole image is one.
+    void SetPanels(const std::vector<PanelBox> &in_panels) { panels = in_panels; }
+
     // The whole image on the host - on the GPU copied there first, where it was not already.
     virtual const int32_t *HostImage();
 private: