core: scroll-settle-pixel - #948

work#606 verify by macos/claude is clean (plain merge, testFrame keeps both the settle row capture and the release-velocity capture). windows/codex and windows/agy list no findings: their failures are the Windows box's known baseline (integration 83/87 on main too; the Server.test crash is work#553). CI green at head. The frame capture stays the PM follow-up as ruled. Basis: work#575.