fix(editor): render <br> in markdown table cells as line breaks in rich mode

[xianjianlf2]

Fixes #8838. In the rich Markdown editor (the default .md view), inline HTML tags are encoded into inert raw-HTML atoms that display the literal tag text. For <br>/<br/> inside a table cell — where a blank-line break is impossible — this rendered raw <br> instead of breaking the line.

This renders <br> raw-inline nodes as real break elements while renderMarkdown still emits the verbatim tag, so the value round-trips exactly on save. A native hardBreak is deliberately avoided: it serializes to a space inside table cells and would silently drop the tag. The raw-source node's parse/render DOM logic is extracted into a small dedicated module for cohesion.

Note: the fix is in the Rich editor, not the read-only Preview (which already renders <br> correctly via react-markdown) — the Rich view is what the report's "preview mode" refers to as the default rendered surface.

Tested: new raw-markdown-html-line-break.test.ts covers break rendering, literal-span preservation, and verbatim round-trip; 101 related rich-markdown tests pass.

Closes #8838

X: @mark86202384100

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds shared parsing and rendering helpers for raw Markdown HTML source nodes, including preservation of authored <br> spellings and rendering them as real br elements. Updates the raw HTML editor node to use these helpers. Adds tests covering table-cell line breaks, inert non-break inline HTML, and Markdown serialization of <br> and <br/>.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description explains the fix, but it omits the repository's required Summary, Screenshots, Testing, review, security, and Notes sections.	Rewrite the PR description using the full template and fill in each required section, including screenshots or 'No visual change' and the checklist items.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: rendering tags as line breaks in rich Markdown table cells.
Linked Issues check	✅ Passed	The code and tests address #8838 by rendering tags as line breaks in table cells and preserving verbatim round-tripping.
Out of Scope Changes check	✅ Passed	The changes stay focused on the linked bug fix, shared DOM helpers, and regression tests with no unrelated additions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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🧹 Nitpick comments (1)

src/renderer/src/components/editor/raw-markdown-html-source-dom.ts (1)

17-21: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Consider exporting the private type RawMarkdownSourceParseRule.

The rawMarkdownSourceParseRules function is exported but returns an array of RawMarkdownSourceParseRule, which is a private type. Depending on the TypeScript configuration (e.g., declaration: true or isolatedModules), this can cause a TS4023 or TS4081 compilation error.

Consider either exporting the RawMarkdownSourceParseRule type or using ProseMirror's built-in ParseRule type from @tiptap/pm/model to ensure full type-safety and avoid private-type emission errors.

💡 Proposed fix

-type RawMarkdownSourceParseRule = {
+export type RawMarkdownSourceParseRule = {
   tag: string
   priority?: number
   getAttrs: (element: HTMLElement) => { value: string }
 }

Also applies to: 37-40

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 64f7f322-cbb0-4c8e-a57e-fddd8cacecde

📥 Commits

Reviewing files that changed from the base of the PR and between cf02cc4 and af48c13.

📒 Files selected for processing (3)

• src/renderer/src/components/editor/raw-markdown-html-line-break.test.ts
• src/renderer/src/components/editor/raw-markdown-html-source-dom.ts
• src/renderer/src/components/editor/raw-markdown-html.ts