CLAUDE: Clamp corr_offset_scale in refineMotionVectors to not exceed scan range

corr_offset_eff is now computed after corr_pairs_ref so the upper bound
(corr_pairs_ref / corr_offset) is available; lower bound kept at 1.
Clamping is flagged in the existing println when it activates.
Co-authored-by: Claude <claude@elphel.com>

src/main/java/com/elphel/imagej/cuas/CuasMotion.java

@@ -2064,14 +2064,7 @@ public class CuasMotion {
 			String              dbg_suffix,
 			int                 dbg_iter_index,     // to generate different image names for different iteration to simplify "save as" images
 			int                 debugLevel) {
-		// TODO: limit corr_offset_scale so corr_offset_eff will not exceed scan range (but keep >=1)
-		
 		final int max_index_dbg = 5; // show images for the first iterations only
-		// By Claude on 05/13/2026: scale corr_offset for residual measurement.
-		// S>1 uses larger frame separation (better SNR for small residuals); result is divided by S to normalize.
-		// offset_scale for mask positioning and corr_offset_mv in correlatePairs stay on original corr_offset.
-//		final int corr_offset_scale = (int) Math.round(recalc_mv_boost); // TODO: promote to config or derive from other params
-		final int corr_offset_eff   = corr_offset * corr_offset_scale;
 		final int tileSize = GPUTileProcessor.DTT_SIZE;   // 8 pixels
 		final int tilesX   = cuasMotion.tilesX;
 		final int width    = cuasMotion.gpu_max_width;
@@ -2085,13 +2078,17 @@ public class CuasMotion {
 
 		// Boosted pair count, centered on frame_center
 		final int corr_pairs_ref = (int) Math.round(2 * half_accum_range * recalc_mv_boost);
+		// By Claude on 05/14/2026: clamp corr_offset_scale so corr_offset_eff <= corr_pairs_ref (keep >=1)
+		final int corr_offset_eff = corr_offset * Math.max(1, Math.min(corr_offset_scale, corr_pairs_ref / corr_offset));
 
 		// Hard-coded debug selectors: set >= 0 to enable per-scan/per-tile visualisation
 		final int dbg_nseq = 97; // 40; // 41; // 157; // -(116); // 57; // 20; // -1;
 		final int dbg_tile = 54+38*80; //52+38*80;  // 50+38*80; // 55+38*80; // -(17 + 33*80); // 48+32*80; // 50+38*80; // -1;
+		final int corr_offset_scale_eff = corr_offset_eff / corr_offset; // actual scale after clamping
 		if (debugLevel >= 0) {
 			System.out.println("refineMotionVectors(): corr_offset="+corr_offset+", corr_offset_scale="+corr_offset_scale+
 					", corr_offset_eff="+corr_offset_eff+
+					(corr_offset_scale_eff != corr_offset_scale ? " (CLAMPED from "+corr_offset_scale+" to "+corr_offset_scale_eff+")" : "")+
 					", dbg_nseq="+dbg_nseq+", dbg_tile="+dbg_tile);
 		}
 		// Pre-compute integer-pixel raised-cosine mask kernel once (shared across all nseq)