[FEATURE]: Add node-based dialogue preview view to display each user's messages as connected nodes

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Proposal: Add a node-based "dialogue preview" view that renders each user message/question as a distinct node connected by lines to indicate sequence and reply relationships.

Motivation:

• Makes long or branching conversations easy to scan and understand.
• Lets users quickly preview every question they asked and others asked during a session.
• Facilitates navigation (jump to any message) and review/debugging of conversation flows.

Suggested capabilities:

• One node per user message showing username and timestamp (compact view) and hover to preview full content.
• Lines to indicate chronological flow and explicit reply/branch relationships; support linear and branched layouts (left-to-right or top-to-bottom).
• Click a node to focus the main chat view on that message.
• Collapse/expand sections of the graph for long conversations and an optional filter to show only messages from the current user.
• Accessibility: keyboard navigation, screen-reader labels for nodes, and high-contrast colors.

Implementation notes / UX ideas:

• Provide toggle between the regular chat list and the node view.
• Represent replies as branches; edits or deletions update the graph in-place.
• Offer export/print of the node view for sharing session flows.

中文摘要：在对话界面增加“节点视图”，以节点+连线表示每个用户的提问，便于预览、定位与理解对话结构。