develop
fix: preserve Google Docs CSS formatting on paste (#4699)
fix(muya): show and slug TOC headings by rendered plain text (#3516) (#4811)
fix(muya): editor parity with muyajs (themes, fonts, spellcheck) + CLASS_NAMES cleanup (#4454)
fix(muya): skip identity operations during deferred flush (#4815)
fix(muya): isolate mermaid render failures during export (#4812) (#4840)
refactor(muya): treat the code fence info string as the source of truth (CommonMark) (#4856)
fix(export): repair five styled-HTML export regressions (math, vega, footnotes, TOC, images) (#4576)