fix(editor): keep visual line clicks aligned

[murongg]

Summary

• move heading, paragraph, and blockquote rhythm from editable line padding/margins into measured CodeMirror block spacers
• pass configurable paragraph spacing into the editor height model while preserving the existing visual spacing
• keep ordinary inline input on a mapped fast path and rebuild spacing only for block-structural changes
• add regression coverage for heading levels, paragraph preferences, blockquotes, blank-line edits, and syntax-scan performance

Why

CodeMirror maps pointer coordinates through a virtual height model. Vertical padding and margins applied directly to editable lines were not represented reliably in that model, so the rendered document became taller than CodeMirror expected and clicks landed on later lines. The drift accumulated in heading-rich documents on both desktop and web.

Validation

• cd packages/editor && pnpm test && pnpm build && pnpm typecheck:test — 39 test files and 511 tests passed
• cd packages/app && pnpm exec vitest run src/styles.test.ts src/components/CodeMirrorPaperSurface.test.tsx --environment jsdom --globals && pnpm build && pnpm typecheck:test — 2 test files and 105 tests passed
• browser QA with the issue attachment confirmed clicks on 3.1.1, 3.1.2, and quoted paragraph rows keep the caret on the clicked visual line
• git diff --check passed

Risk

• the change adds measured editor-only decorations; Markdown content, saved files, clipboard output, and exports are unchanged
• paragraph spacing remains configurable and is reconfigured without recreating the editor view

Screenshots

Not included because the intended visual spacing is unchanged; this fixes pointer-to-caret alignment.

Closes #700

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Project	Deployment	Actions	Updated (UTC)
markra-web	Ready	Preview	Aug 28, 2026 10:44am