refactor(deep-research): replace case study company with ByteDance example

Replace \"深度推理（上海）科技有限公司\" with \"字节跳动子公司\"
as the case study example to avoid exposing user's own company info.

Also update .gitignore to exclude:
- deep-research-output/ (contains sensitive research data)
- recovered_deep_research/
- .opencli/
- douban-skill/ (work-in-progress)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -82,3 +82,13 @@ INSTALLATION.md
 seo-expert/
 video-creator/
 /jsonl-viewer/
+
+# Research output (may contain sensitive data)
+deep-research-output/
+recovered_deep_research/
+
+# OpenCLI cache
+.opencli/
+
+# Work-in-progress skills
+douban-skill/