Support double-Enter continuation prompts

Summary

Codex should support a fast continuation gesture: double-tap Enter to inject and send a lightweight continuation prompt automatically.

Problem

When a session is already flowing, the user often wants to nudge Codex to continue without restating intent manually. Right now that requires typing another prompt each time, even when the continuation intent is obvious.

Requested behavior

• Double-tap Enter to send a continuation prompt automatically
• The inserted continuation prompt can be chosen from a small rotating set such as:
• let's keep going
• let's roll
• keep it comin
• now we're on a roll
• lets rock n roll
• keep it groovin
• continuous on our way to the dancefloor
• The message should behave like a normal user continuation prompt once sent
• The feature should be optional/configurable if needed, but the core request is the interaction pattern itself

Success criteria

• A rapid double-Enter sends a continuation prompt without manual typing
• The behavior is reliable and does not conflict with ordinary single-Enter send behavior
• The inserted prompt is visible/auditable in the conversation history

Related context

This is related to, but narrower than, a broader continuation-hint system request covering contextual follow-up hints, ephemeral refresh prompts, and a shared annotation/intention pass.