Closes #5773

Summary

Inline code used a fixed font stack while code blocks respected the configured code font, allowing different CJK fallback fonts. Both now share --mu-code-font-family and the same default stack, with rules kept in the existing editor and export stylesheets. HTML/PDF exports use the same font-family behavior and preserve the editor's code font configuration.

Font sizes, line heights, backgrounds, and other independent styles remain unchanged. No new preference is introduced.

Type of change

• Bug fix (non-breaking, fixes an issue)
• New feature (non-breaking, adds functionality)
• Breaking change (causes existing functionality to change)
• Documentation update

Test plan

• New tests added
• Manually tested on: automated Chromium checks on macOS; no manual UI pass

Passed:

• 8 Chromium tests covering shared fonts, all bundled editor themes, default/academic/liber export themes, custom fonts, screen/print styles, PDF generation, and existing code font/size/wrapping behavior. Actual CJK glyph fonts are checked through Chromium's font inspection API.
• 20 setOptions unit tests.
• Root ESLint and typecheck; Muya typecheck and ESLint for changed TypeScript files.
• Stylelint for the export stylesheet; git diff --check.

Notes for reviewers

The full check of touched CSS files still reports pre-existing selector-order errors in blockSyntax.css and inlineSyntax.css. Existing lint warnings also remain.

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.