fix: address markdown renderer review findings

Restore the replaced pipeline's synthetic fence newline so a real trailing
blank line inside a fence survives CodeBlock's display trim, and pin it
plus header-only tables in the DOM-parity corpus. Route
extractMarkdownPlainText through parseGfm so the grammar has one source.
Document the fixture provenance check (all 46 fixtures reproduce
byte-identically from react-markdown at 9e8101b800), the deliberate
O(prefix) divergence memcmp, the per-arm scope of grammar consistency,
the React 18 MathML namespace limitation, and the prefix-equivalence
corpus constraint.

.agents/notes/implemented/architecture/2026-08-06-web-markdown-incremental-ast-renderer.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/architecture/2026-08-06-web-markdown-incremental-ast-renderer.md
-2026-08-06-web-markdown-incremental-ast-renderer.md: 98d28fa27f8e6e4b5f2ac21831c8f80f8c0c3631
-2026-08-06-web-markdown-incremental-ast-renderer.zh.md: c2c19fe36b8290c1802f6e2b321336e1a68d686f
+2026-08-06-web-markdown-incremental-ast-renderer.md: 3599bfcc78dc4eefe5e82f461a469bdba15f3aae
+2026-08-06-web-markdown-incremental-ast-renderer.zh.md: 2e00977da58ef29a77c45abcecf0f3bb62737929

.agents/notes/implemented/architecture/2026-08-06-web-markdown-incremental-ast-renderer.md

@@ -14,7 +14,7 @@ English | [中文](2026-08-06-web-markdown-incremental-ast-renderer.zh.md)
 
 - **Grammars** ([parse.ts](../../../../packages/client/ui-primitives/src/markdown/parse.ts)): `parseGfm` (streaming arm and `extractMarkdownPlainText`) and `parseGfmWithMath` (settled arm) call `mdast-util-from-markdown` with the same micromark extensions the replaced remark plugins wrapped, so block boundaries are identical everywhere. `mathCompatibility` (ex `remarkMathCompatibility`) now exports its micromark extension directly.
 - **Incremental parsing** ([incremental.ts](../../../../packages/client/ui-primitives/src/markdown/incremental.ts)): CommonMark block parsing is line-based, so appended text reshapes only the parse frontier. `IncrementalMarkdownParser` keeps the trailing two blocks unstable (the last block is the frontier; the second-to-last is safety margin), freezes everything before them, and re-parses only the source tail from the last frozen block's `position.end.offset` — the parser's own offsets, no bespoke source scanning. Each source region parses O(1) times per stream instead of once per chunk; a single giant block (an unclosed fence) degrades to the old full-reparse cost and no worse. Non-append input resets the state under a bumped generation.
-- **Rendering** ([render.tsx](../../../../packages/client/ui-primitives/src/markdown/render.tsx), [katex.tsx](../../../../packages/client/ui-primitives/src/markdown/katex.tsx)): one switch over mdast node types replaces remark-rehype + react-markdown, reproducing the replaced pipeline's DOM byte-for-byte — table alignment as `text-align` styles, tight-list paragraph unwrapping, task-list classes and checkbox spacing, the footnote section (whose in-page anchors the protocol allowlist already reduced to plain text), literal raw HTML, the separator newlines that surface next to literal HTML text, and rehype-katex's three-arm error chain with KaTeX HTML mapped to React through the browser's own `DOMParser` (no wrapper element, so first/last-child margin rules still reach `.katex-display`). Frozen blocks cache their React elements and keep source-offset keys, so crossing the freeze boundary reconciles instead of remounting; `MarkdownText` is memoized.
+- **Rendering** ([render.tsx](../../../../packages/client/ui-primitives/src/markdown/render.tsx), [katex.tsx](../../../../packages/client/ui-primitives/src/markdown/katex.tsx)): one switch over mdast node types replaces remark-rehype + react-markdown, reproducing the replaced pipeline's DOM byte-for-byte — table alignment as `text-align` styles, tight-list paragraph unwrapping, task-list classes and checkbox spacing, the footnote section (whose in-page anchors the protocol allowlist already reduced to plain text), literal raw HTML, the separator newlines that surface next to literal HTML text, and rehype-katex's three-arm error chain with KaTeX HTML mapped to React through the browser's own `DOMParser` (no wrapper element, so first/last-child margin rules still reach `.katex-display`; React 18 puts the `.katex-mathml` subtree in the HTML namespace exactly as the replaced pipeline did — a pre-existing limitation outside this parity contract, invisible to the visual `.katex-html` arm). Frozen blocks cache their React elements and keep source-offset keys, so crossing the freeze boundary reconciles instead of remounting; `MarkdownText` is memoized.
 
 The DOM is pinned by `tests/fixtures/markdown-dom`: fixtures recorded from the react-markdown implementation before the swap, which the new renderer must reproduce under a whitespace-normalizing serializer. A fixture diff is a user-visible markdown style change to review, never to re-record for a refactor. `tests/markdown-incremental.spec.tsx` holds the equivalence property — at every appended prefix, chunked at 1/3/7/16 bytes, the live component's DOM equals a fresh mount's — plus freeze-boundary DOM-node identity and reset behavior.
 

.agents/notes/implemented/architecture/2026-08-06-web-markdown-incremental-ast-renderer.zh.md

@@ -14,7 +14,7 @@ Status: implemented
 
 - **语法**([parse.ts](../../../../packages/client/ui-primitives/src/markdown/parse.ts)):`parseGfm`(流式臂与 `extractMarkdownPlainText`)和 `parseGfmWithMath`(定稿臂)以被替换的 remark 插件所包装的同一组 micromark 扩展调用 `mdast-util-from-markdown`,因此各处块边界完全一致。`mathCompatibility`(原 `remarkMathCompatibility`)现在直接导出其 micromark 扩展。
 - **增量解析**([incremental.ts](../../../../packages/client/ui-primitives/src/markdown/incremental.ts)):CommonMark 块解析按行推进,追加文本只会重塑解析前沿。`IncrementalMarkdownParser` 保留末尾两个块不稳定(最后一块是前沿;倒数第二块是安全裕量),冻结其前的所有块,只从最后一个冻结块的 `position.end.offset` 起重新解析源尾部——用的是解析器自己的偏移量,没有任何自制源扫描。每个源区间在整个流中解析 O(1) 次而非每 chunk 一次;单个巨型块(未闭合围栏)退化为旧的全量重解析成本,不会更差。非追加输入在递增的 generation 下重置状态。
-- **渲染**([render.tsx](../../../../packages/client/ui-primitives/src/markdown/render.tsx)、[katex.tsx](../../../../packages/client/ui-primitives/src/markdown/katex.tsx)):一个对 mdast 节点类型的 switch 取代 remark-rehype + react-markdown,逐字节复刻被替换管线的 DOM——表格对齐渲染为 `text-align` 样式、紧凑列表段落解包、任务列表类名与复选框空格、脚注区(其页内锚点本就被协议白名单降为纯文本)、字面 raw HTML、会与字面 HTML 文本相邻显形的分隔换行,以及 rehype-katex 的三臂容错链,KaTeX HTML 经浏览器自带的 `DOMParser` 映射为 React(无包裹元素,首/末子元素的 margin 规则仍能作用于 `.katex-display`)。冻结块缓存其 React 元素并保持源偏移 key,跨过冻结边界时走 reconcile 而非重挂载;`MarkdownText` 已 memo 化。
+- **渲染**([render.tsx](../../../../packages/client/ui-primitives/src/markdown/render.tsx)、[katex.tsx](../../../../packages/client/ui-primitives/src/markdown/katex.tsx)):一个对 mdast 节点类型的 switch 取代 remark-rehype + react-markdown,逐字节复刻被替换管线的 DOM——表格对齐渲染为 `text-align` 样式、紧凑列表段落解包、任务列表类名与复选框空格、脚注区(其页内锚点本就被协议白名单降为纯文本)、字面 raw HTML、会与字面 HTML 文本相邻显形的分隔换行,以及 rehype-katex 的三臂容错链,KaTeX HTML 经浏览器自带的 `DOMParser` 映射为 React(无包裹元素,首/末子元素的 margin 规则仍能作用于 `.katex-display`;React 18 会把 `.katex-mathml` 子树放进 HTML 命名空间,与被替换管线完全一致——既有限制,不在本对等性契约范围内,对承担视觉渲染的 `.katex-html` 臂不可见)。冻结块缓存其 React 元素并保持源偏移 key,跨过冻结边界时走 reconcile 而非重挂载;`MarkdownText` 已 memo 化。
 
 DOM 由 `tests/fixtures/markdown-dom` 钉死:fixture 录制自替换前的 react-markdown 实现,新渲染器必须在空白规整序列化器下复现。fixture 差异即用户可见的 markdown 样式变更,必须按此评审,绝不能为重构而重录。`tests/markdown-incremental.spec.tsx` 承载等价性性质——以 1/3/7/16 字节分块,在每个追加前缀处,常驻组件的 DOM 都等于全新挂载——外加冻结边界的 DOM 节点同一性与重置行为。