1. resize() now clamps anchorSubRow using exact wrap count instead of ceil(displayWidth/columns) estimate, which undercounts when boundary waste from wide characters increases actual sub-row count. 2. _recomputeCurrentEstimate() clamps currentEstimatedVisualRow to [0, totalEstimatedVisualRows-1] so the scrollbar invariant holds even when exact wrap counts exceed the estimate. 3. computeWrapPoints() no longer emits wrap point at index 0 when the first visible character is wider than columns — the character overflows its row instead of creating an empty first sub-row. Adds 4 regression tests covering all three fixes.