fix(semantic): preserve repository hierarchy in overviews

[chethanuk]

Summary

• tighten overview generation guidance so child directories are treated as parts of the same repository by default
• strengthen prompt regression coverage for repository hierarchy rules
• keep the change scoped to the overview prompt and test coverage

Testing

• pytest tests/storage/test_semantic_processor_language.py -v

Fixes #1269

[github-actions]

PR Reviewer Guide 🔍

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🎫 Ticket compliance analysis ✅ 1269 - Fully compliant Compliant requirements: 添加了 overview 生成的关系规则，引导将子目录视为同一仓库的一部分 新增测试验证关系规则存在于 prompt 中

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🏅 Score: 95

🧪 PR contains tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ No major issues detected

[github-actions]

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