Get rid of column limit in markdown files

The column limit made sense in the original document, since it was read in its raw source form. However, modern Pan Docs are instead processed.

The column limit is currently not respected everywhere, anyway... and it's actually harmful, since it means that changes are not localized to where changes are actually made, but also bleed into neighboring lines when re-balancing everything.

Since (single) line breaks are entirely ignored in Markdown (and mdBook certainly does), I suggest we split semantically instead, i.e. one line break after every sentence. 80-column editors are rare nowadays, and soft-wrapping what is mostly prose isn't nearly as jarring as doing so with code.

Start by locating the Markdown files and the current column-limit or line-wrapping convention, then check how mdBook processes their line breaks. Review the issue's proposed sentence-per-line style across the documentation. Done means the relevant Markdown no longer requires fixed-width rebalancing while rendering remains unchanged.

Written by the indexing model from the issue text.