feat: add citation/reference support to deep research reports (#1143)

* feat: add citation/reference support to deep research reports (#1141)

- Enhance lead agent system prompt with mandatory citation requirements
  after web_search/web_fetch tool usage
- Add citation examples and best practices to GitHub Deep Research skill
- Add citation hints to report template (Executive Summary, Key Analysis)
- Style regular markdown links in frontend for visual distinction
  (color, underline, hover effect)
- Fix TitleMiddleware being registered when title generation is disabled

* fix: address PR review comments

- Revert TitleMiddleware conditional registration (agent.py) to avoid
  sync/async incompatibility with DeerFlowClient
- Fix markdown link rendering: merge classNames instead of overwriting,
  only set target=_blank for external http(s) URLs
- Remove unrelated package.json/pnpm-lock.yaml changes

* fix: use plain markdown links in Sources section for cleaner rendering

Inline citations in report body use [citation:Title](URL) for pill/badge style.
Sources section uses plain [Title](URL) for simple underlined link style.

* fix(frontend): render plain links as underlined text in artifact markdown

Only links with citation: prefix render as Badge pills.
Regular links in Sources section now render as underlined text links.

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

skills/public/github-deep-research/SKILL.md

@@ -147,5 +147,20 @@ Save report as: `research_{topic}_{YYYYMMDD}.md`
 3. **Triangulate claims** - 2+ independent sources
 4. **Note conflicting info** - Don't hide contradictions
 5. **Distinguish fact vs opinion** - Label speculation clearly
-6. **Reference sources** - Add source references near claims where applicable
-7. **Update as you go** - Don't wait until end to synthesize
+6. **CRITICAL: Always include inline citations** - Use `[citation:Title](URL)` format immediately after each claim from external sources
+7. **Extract URLs from search results** - web_search returns {title, url, snippet} - always use the URL field
+8. **Update as you go** - Don't wait until end to synthesize
+
+### Citation Examples
+
+**Good - With inline citations:**
+```markdown
+The project gained 10,000 stars within 3 months of launch [citation:GitHub Stats](https://github.com/owner/repo).
+The architecture uses LangGraph for workflow orchestration [citation:LangGraph Docs](https://langchain.com/langgraph).
+```
+
+**Bad - Without citations:**
+```markdown
+The project gained 10,000 stars within 3 months of launch.
+The architecture uses LangGraph for workflow orchestration.
+```

skills/public/github-deep-research/assets/report_template.md

@@ -30,6 +30,9 @@
 
 {EXECUTIVE_SUMMARY}
 
+**IMPORTANT**: Include inline citations using `[citation:Title](URL)` format after each claim. Example:
+"The project gained 10k stars in 3 months [citation:GitHub Stats](https://github.com/owner/repo)."
+
 ---
 
 ## Complete Chronological Timeline
@@ -56,6 +59,8 @@
 
 ## Key Analysis
 
+**IMPORTANT**: Support each analysis point with inline citations `[citation:Title](URL)`.
+
 ### {ANALYSIS_SECTION_1_TITLE}
 
 {ANALYSIS_SECTION_1_CONTENT}