Support split view for Codex conversation threads

Feature request:
When using Codex as a learning-oriented coding assistant, I often read a long previous answer and then ask follow-up questions while studying it.

Currently, if I ask several follow-up questions, I need to keep scrolling back to the original answer to compare the explanation with the new answers. This is especially painful when the original answer contains code, diffs, or step-by-step reasoning.

Request:
Please add a split-view mode for Codex conversations, where the same task can be viewed in two independently scrollable panes.

Example workflow:

  • Left pane: pinned at an earlier answer, such as a generated code explanation.
  • Right pane: continue the live conversation with follow-up questions.
  • Both panes belong to the same task/thread.
  • The user can scroll each pane independently.

Why it matters:
This would make Codex much better for learning, code review, and guided implementation. It would let users keep source explanations visible while asking detailed follow-up questions without losing context.

Possible MVP:

  • Add “Open conversation in split view”
  • Allow one pane to stay pinned at a selected message
  • Continue normal conversation in the other pane