Support adding "Tags" or "Bookmarks" within a single conversation for quick navigation

Is your feature request related to a problem? Please describe.
I often find myself having very long conversations that cover multiple distinct topics or distinct phases of coding (e.g., "Requirement Analysis," "Database Design," "Bug Fixing").

Currently, when I need to review or study these long conversations later, it is very difficult to locate specific topics. I have to scroll up and down repeatedly to find the exact part where a specific topic was discussed.

Describe the solution you'd like
I would like to request a feature that allows users to add Tags, Labels, or Bookmarks to specific messages within a chat thread.

Ideally, it would work like this:

1. Tagging: Right-click or hover over a message to add a custom tag (e.g., "Login Logic," "API Error Fix").
2. Navigation: Have a sidebar or a dropdown menu that lists all the tags in the current conversation.
3. Jumping: Clicking on a tag in the list immediately scrolls the view to that specific message.

Describe alternatives you've considered
Currently, I have to use the browser's "Find" (Cmd+F) feature to search for keywords, but this is inefficient if I don't remember the exact wording I used.

Additional context
This feature would be extremely helpful for users who use the tool for deep learning and reviewing complex coding sessions. It acts like a "Table of Contents" for a long conversation.

Thanks for your hard work on this project!

The issue names no files, tests, or entry points. Start by tracing how the Python CLI produces HTML or Markdown and how messages are represented in the rendered conversation; done means users can create tags or bookmarks, list them within a conversation, and jump to the associated message as described.