Prettier is no longer a project dependency and oxc.oxc-vscode handles formatting for all file types the project touches. Switch [json], [jsonc], [markdown], [mdx], and [yaml] formatters from esbenp.prettier-vscode to oxc.oxc-vscode (oxfmt under the hood, Prettier-compatible for JS/TS and native for JSON/MD/YAML). Drop 'esbenp' from cspell dictionary (no longer referenced).