perf(markdown): cache completed streaming blocks

[c121914yu]

Summary

• split streaming Markdown into root-level blocks and memoize completed blocks
• keep the existing tail-only fade on the active block
• preserve cross-block reference links and GFM footnotes by falling back to full-document rendering

Verification

• pnpm exec vitest run -c vitest.config.ts test/components/Markdown/streamMarkdownBlocks.test.ts test/components/Markdown/rehypeStreamAnimated.test.ts test/components/Markdown/utils.test.ts --run --coverage=false
• app test suite: 150 test files passed; the 8 initial sandbox-adapter resolution failures passed after building the local workspace package
• targeted ESLint and Prettier checks passed

No documentation changes.

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	18.43%	1632 / 8855
🔵	Statements	18.41%	1713 / 9300
🔵	Functions	16.21%	342 / 2109
🔵	Branches	15.1%	759 / 5024

File Coverage

No changed files found.

Generated in workflow #1407 for commit a584507 by the Vitest Coverage Report Action

[github-actions]

✅ Admin Preview Image Ready!

ghcr.io/labring/fastgpt-pr:admin_a584507d9b4f14b76b2ac61385cb236253723de8

🕒 Time: 2026-07-14 21:12:06 (UTC+8)

[github-actions]

✅ Build Successful - Preview fastgpt Image for this PR:

ghcr.io/labring/fastgpt-pr:fastgpt_a584507d9b4f14b76b2ac61385cb236253723de8

🕒 Time: 2026-07-14 21:14:28 (UTC+8)

[Copilot]

Pull request overview

This PR improves streaming Markdown rendering performance in the app by splitting streamed Markdown into root-level blocks and memoizing completed blocks so only the actively-growing block re-renders. It maintains the existing “tail-only” fade animation on the active block and preserves correctness for cross-block reference links / GFM footnotes by falling back to full-document rendering when those constructs are present.

Changes:

• Add a splitMarkdownBlocks utility that parses Markdown and slices the source into stable root-level blocks (with a full-document fallback for references/footnotes).
• Update the Markdown renderer to render blocks via a memoized MarkdownStreamBlock, applying the streaming tail animation only to the last block.
• Add unit tests for block splitting behavior and rendering equivalence, and add required parser dependencies.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
projects/app/test/components/Markdown/streamMarkdownBlocks.test.ts	Adds tests covering block splitting rules, offsets, and render equivalence across block rendering vs full-document rendering.
projects/app/src/components/Markdown/streamMarkdownBlocks.ts	Implements Markdown root-level block splitting using unified + remark-parse with math/GFM support and fallbacks for references/footnotes/whitespace-only input.
projects/app/src/components/Markdown/index.tsx	Refactors streaming rendering to memoize completed blocks and keep tail fade on the active (last) block.
projects/app/package.json	Adds direct dependencies needed for parsing (remark-parse, unified).
pnpm-lock.yaml	Updates lockfile for the newly added dependencies.

Files not reviewed (1)

• pnpm-lock.yaml: Generated file

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