The version record turns light, and markdown emphasis stops eating its own links

Three fixes, all of them visible on the version record↗ and two of them bugs that had been shipping since v1.0.0.

• The version record is on the paper theme. It inherited the dark theme of the dev page it used to be, which is the wrong ground for the longest continuous prose on the site. Every rule on that page routes through its tokens, so the page turned over by changing six token values and two code-span backgrounds — nothing else moved.
• Emphasis now nests. A strong or em run carried a flat string, so a link or a code span inside **bold** was never parsed and the reader saw the markdown source — brackets, parentheses and all — on a published page. Runs carry children now and both the parser and the renderer recurse. Nesting is capped at four deep, which is three more than any release note will ever need.
• *single asterisk italics* are supported. The parser handled _underscores_ only, so every *emphasis* in the previous two releases' notes rendered as literal asterisks. The **bold** branch is still matched first, so nothing is ambiguous.
• And the notes' own links were pointing one directory too high. They render at /versions.html, so a ../ in a note escapes the site root. Fixed in the two notes that had it.

A tool, because this was the second time. scripts/site/sync-modules.mjs pushes a change to a shared module — dom, nav, menu, io, markdown — into every page that carries a copy, from one source per module under scripts/site/modules/. Each page inlining its own copy is the price of having no build step, and the cost is that fixing dom.js means fixing it in thirty-one places. --check now runs as a CI gate, so a hand-edit applied to one page and not the rest fails the build instead of shipping.

scripts/migrate/modules/ is deliberately left alone: it is the frozen record of what produced v1.0.0, and editing it would break the claim that re-running the migration reproduces that snapshot.