Release 1.2.0

[JeroenDeDauw]

• A ConvertToMarkdownModel maintenance script converts existing wikitext pages to the Markdown content
  model, selecting them by .md suffix and/or namespace, the same way the activation settings select new
  pages. It changes the content model rather than the page text, skips redirects, and supports --dry-run
• Fenced code blocks whose info string names a language are now syntax highlighted, the same way a wikitext
  <syntaxhighlight> block is. This needs the SyntaxHighlight extension (bundled with MediaWiki) to be
  installed; without it, code blocks keep rendering as plain preformatted text
• Code blocks no longer get a background pill behind each of their lines, which happened because skins style the
  code element for inline use and CommonMark nests it inside pre
• A thumb file embed alone on its line now renders as a standalone framed thumbnail rather than being wrapped
  in a paragraph, which produced invalid HTML5 and a stray empty paragraph
• A thumb embed of a missing file now renders the framed box with its caption and an upload link, the way
  wikitext does, instead of a bare upload link that silently dropped the caption
• Thumbnail embeds now load the same media module MediaWiki loads for wikitext thumbnails, so their magnify
  affordance works

extension.json was already bumped to 1.2.0 on master, so this only dates the release-notes heading.

_{AI-authored — Claude Code, Opus 4.8 (1M context) (max); @JeroenDeDauw asked for the release, starting by checking the notes were current; not yet human-reviewed; verified every commit since the 1.1.0 tag is represented in the notes (docs-only and version-bump commits aside) and that no i18n or compatibility changes need a bullet; release-notes date only, no code change.}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.34%. Comparing base (8612d51) to head (404b10a).

Additional details and impacted files

@@            Coverage Diff            @@
##             master      #46   +/-   ##
=========================================
  Coverage     83.34%   83.34%           
  Complexity      417      417           
=========================================
  Files            40       40           
  Lines          1069     1069           
=========================================
  Hits            891      891           
  Misses          178      178           

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