fix(editor): resolve code block interaction issues

[murongg]

Summary

• preserve surrounding rich text when pasted HTML contains both prose and code
• unwrap fenced code blocks safely when Backspace is pressed at the first code line, including multi-cursor handling
• add a persistent editor preference for showing code block line numbers, with localized settings copy
• remove the gutter, divider, and hanging indent across the full code block when line numbers are hidden

Validation

• cd packages/editor && pnpm test && pnpm build && pnpm typecheck:test passed (413 tests)
• cd packages/app && pnpm test && pnpm build && pnpm typecheck:test passed (1,484 tests)
• cd packages/shared && pnpm test passed (62 tests)
• cd packages/shared && pnpm build passed
• pnpm build passed for all workspace projects, including web and desktop production builds
• browser QA confirmed hidden line numbers use a 16px content inset with no pseudo-element, hanging indent, or gutter gradient on the top, content, and closing rows

Risk

• the new preference defaults to enabled, preserving existing rendering
• the Backspace handler only intercepts empty selections at the first fenced-code content position; other selections retain standard editor behavior
• code block gutter styling is now keyed to an explicit renderer state so wrapped rows and block edges change together

Closes #631

[vercel]

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Project	Deployment	Actions	Updated (UTC)
markra-web	Ready	Preview	Aug 3, 2026 2:14am