fix(memos-local): scope sharing state by hubInstanceId and fix owner …

[tangbotony]

• Add hubInstanceId to team_shared_chunks, local_shared_tasks, and client_hub_connection to prevent stale sharing state when switching between Hub instances
• Fix memory_search/timeline/get owner isolation by accepting agentId from tool execution context
• Fix viewer sharing queries to use role-appropriate tables (hub_memories vs team_shared_chunks)
• Apply maxChars truncation in memory_get handler
• Fix 11 failing tests: accuracy thresholds, integration env isolation, plugin-impl join flow, and task-processor topic judge flakiness

Description

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Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (does not change functionality, e.g. code style improvements, linting)
• Documentation update

How Has This Been Tested?

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• Unit Test
• Test Script Or Test Steps (please provide)
• Pipeline Automated API Test (please provide)

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

Reviewer Checklist

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• Tests have been provided