Codex Desktop: add a “Promote to chat” button to side conversations

Feature request

Please add a visible Promote to chat action to side conversations in Codex Desktop.

Problem

A side chat can begin as a quick tangent and become substantial architecture, research, or debugging work. The user only discovers afterward that this conversation deserves a durable thread. Today, promoting it means manually copying the transcript or reconstructing the discussion elsewhere.

I hit exactly this workflow: a side chat grew into a complete resource-manager architecture discussion and design plan, and I then wanted to preserve the full conversation as a normal chat.

Requested behavior

A Promote to chat button in the side-chat header or overflow menu should:

1. Create a normal, durable chat containing the complete side-chat transcript.
2. Preserve the inherited context, attachments, workspace association, and relationship to the parent chat.
3. Leave the parent chat unchanged.
4. Immediately open the promoted chat or provide a clear link to it.
5. Make the result appear in normal history and support ordinary resume, rename, pin, fork, and export behavior.
6. Leave the original side chat intact if promotion fails.

This can be an opt-in operation; side chats do not need to become persistent by default. Conceptually, it is the existing fork/persistence machinery applied at the point where an ephemeral side chat becomes valuable.

Why a button matters

The decision cannot reliably be made before starting /side. The promotion action needs to be discoverable exactly when the user realizes the tangent is no longer disposable.

Related broader proposals: openai/codex#20262 and openai/codex#26227. This issue is specifically for the minimal, concrete Codex Desktop affordance.