Switches the code formatter from Prettier to oxfmt for faster formatting performance locally and in CI.

Changes

• Replace prettier and 2 plugins (prettier-plugin-organize-imports, prettier-plugin-pkg) with oxfmt
• Add .oxfmtrc.json matching the existing Prettier settings (singleQuote, trailingComma es5, printWidth 80)
• Import sorting now handled natively by oxfmt (replaces prettier-plugin-organize-imports)
• Package.json sorting disabled to preserve existing field order
• Remove .prettierrc.js and .prettierignore
• Add format:check script, update CI to use it
• Update Renovate config to group oxfmt package
• Remove Prettier VS Code extension recommendation (oxc extension handles formatting)
• Update oxlint.config.ts to remove .prettierrc.js from ignorePatterns

Result

Format runs in ~300ms on 424 files (10 threads).