[MN4][P1] Cross-link mind-map nodes, highlights, notes, and source documents

[evan188199-tech]

Tracked by #10. Local plan: docs/roadmap/marginnote-4.md.

Goal (中文): 把脑图节点、高亮、笔记和源文档连起来。优先用导出里的显式 ID；没有 ID 时做规范化标题/内容匹配并记录置信度。低置信度关联不得当确定事实。

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Feature Request Description

Give MarginNote tools a reliable graph between mind-map nodes, highlights, notes, and source documents.

The current models already have optional highlight_id, note_id, and document_id fields, but the export parser does not systematically recover those links. Teaching answers therefore miss "this highlight sits under this mind-map node on page 42".

Rules:

• Prefer explicit IDs from the export
• If IDs are missing, match normalized titles/content and record a confidence score
• mn_read_note returns the mind-map path for the item
• mn_mindmap returns linked highlights and source documents
• Low-confidence links must not be injected into teaching answers as certain facts

Related Module

Chat

Use Case

When a learner asks about a concept, DeepTutor can read the surrounding highlight, the mind-map branch it belongs to, and the source document/page. If the link is only a guess, the answer says so instead of inventing a location.

Additional Context

Priority: P1
Phase: M2
Status: Planned
Depends on: parser hardening
Blocks: higher-quality Chat and Deep Research citations

Key files

• deeptutor/capabilities/marginnote/data/base.py
• deeptutor/capabilities/marginnote/data/export_adapter.py
• deeptutor/capabilities/marginnote/tools.py

Acceptance criteria

• Explicit export IDs are preferred and preserved.
• Missing IDs fall back to normalized title/content matching with a recorded confidence.
• mn_read_note includes the mind-map path when known.
• mn_mindmap includes linked highlights and documents.
• Low-confidence associations are labeled and never treated as certain facts in prompts or answers.

Success metric
Teachers and research reports can trace a note to its mind-map location and source page, or clearly say the link is uncertain.