Address review finding: keep signed insets unchanged when their sum fits,
scaling opposing insets proportionally only when both in the pair are
non-negative and their sum exceeds the box dimension.
When text insets exceed the shape dimensions (e.g. lIns + rIns > width),
proportionally scale them down so the inner text rectangle remains
bounded within the shape. Prevents off-slide helper shapes with large
insets from having their text center shifted onto the slide canvas.
Layout added the paragraph's start to the running count, so start k set
paragraph by paragraph read 1, 3, 5. A change of start_at between
neighbouring numbered paragraphs now restarts the count, as PowerPoint's
Start at does; the same start on every paragraph still counts on.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>