fix(web): repair malformed strong-emphasis spacing in assistant output

[p421098]

Description

Assistant responses can contain malformed strong-emphasis Markdown such as:

**發布日期： **2026 年 7 月 30 日

CommonMark does not recognize this as strong emphasis because whitespace appears immediately before the closing **, so the raw delimiters remain visible.

This PR:

• repairs the narrow line-start/whitespace-delimited **label: **value pattern by moving the whitespace after the closing delimiter;
• applies the repair only to ordinary text segments rendered by AssistantResponse;
• leaves thinking segments and other user-authored Markdown surfaces unchanged;
• protects fenced code blocks, inline code spans, and math spans;
• keeps valid and incomplete Markdown unchanged;
• makes the repair idempotent and supports multiple occurrences.

The example above becomes:

**發布日期：** 2026 年 7 月 30 日

Related Issues

• None found.

Module(s) Affected

• agents
• api
• config
• core
• knowledge
• logging
• services
• tools
• utils
• web (Frontend)
• docs (Documentation)
• scripts
• tests
• Other: ...

Checklist

• I have read and followed the contribution guidelines.
• My code follows the project's coding standards.
• I have run pre-commit run --all-files and fixed any issues.
• I have added relevant tests for my changes.
• Documentation is not required for this localized rendering fix.
• My changes do not introduce any new security vulnerabilities.

Verification

• pre-commit run --all-files: blocked by existing repository-wide formatting drift and Windows mypy errors for POSIX-only APIs outside this change
• npm run test:node: 390 passed
• npm run lint: 0 errors; 56 pre-existing warnings in untouched files
• npx tsc --noEmit: passed
• npm run build: passed
• pre-commit run --files web/components/common/AssistantResponse.tsx web/lib/markdown-display.ts web/tests/markdown-display.test.ts: passed
• git diff --check: passed

Additional Notes

The normalization is intentionally not added globally to normalizeMarkdownForDisplay(). Restricting it to assistant text avoids changing user notes, CoWriter content, thinking blocks, or other strict Markdown surfaces.