feat: enhance retriever, reorganizer & NebulaGraph handling

[CaralHsi]

Description

Summary:

• 🔧 NebulaGraph pool & query execution improved:

  • Added reset_pool() for emergency session reset
  • Enhanced session expiration handling & logging

• 🌳 TreeTextMemory major updates:

  • Improved clustering logic & min_group_size adjustments
  • Added cycle detection in convert_graph_to_tree_forworkmem

• 🔍 Retrieval pipeline upgraded:

  • Enhanced BochaSearch parsing (AI Search & Web Search)
  • Internet retriever now defaults to AI search, adds context

• 📝 Prompt & template improvements:

  • Rewrote MEMOS_PRODUCT_BASE_PROMPT and MEMOS_PRODUCT_ENHANCE_PROMPT
  • Clarified memory reference format in responses

• ⚙️ Parameter tuning:

  • Adjusted memory size limits (WorkingMemory, LongTermMemory, UserMemory)
  • Tweaked scheduler thresholds, cluster sizes, and min_group_size

Fix: #(issue)

Docs Issue/PR: (docs-issue-or-pr-link)

Reviewer: @(reviewer)

Checklist:

• I have performed a self-review of my own code | 我已自行检查了自己的代码
• I have commented my code in hard-to-understand areas | 我已在难以理解的地方对代码进行了注释
• I have added tests that prove my fix is effective or that my feature works | 我已添加测试以证明我的修复有效或功能正常
• I have created related documentation issue/PR in MemOS-Docs (if applicable) | 我已在 MemOS-Docs 中创建了相关的文档 issue/PR（如果适用）
• I have linked the issue to this PR (if applicable) | 我已将 issue 链接到此 PR（如果适用）
• I have mentioned the person who will review this PR | 我已提及将审查此 PR 的人