Preserve paragraph breaks after a ParaStyle tag starts the story so leading empty paragraphs and their styles survive Tagged Text import.
Validated individually and after #638 with all six cargo xtask ci gates (1,278 tests passed, four existing tests ignored, 15 WASM compilation checks), six independent paragraph/header/Unicode probes, and an actual export-to-placement command smoke test.
Refs #641
Move and mirror segment midpoints when reversing gradient stops so reversed gradients preserve color and opacity interpolation.
Validated locally on macOS with all six cargo xtask ci gates (1,277 tests passed, four existing tests ignored, 15 WASM compilation checks), plus independent regressions, undo/redo, native and IDML round trips, and PNG/PDF rendering.
Refs #638
Jason Brashear