[Idea] One-click ▶ Continue: turn Send into Continue when a turn stopped and the composer is empty (like Codex)

[furkancak1r]

Proposal

When a turn has stopped (interrupted by the user, or ended on its own e.g. max-tokens) and the composer is empty, turn the primary Send button into a ▶ Continue button. One click sends continue (ideally a localized / configurable text) so the agent resumes where it left off. This is how the Codex app behaves, and it removes the most common "type continue + Enter" loop.

Visibility rules

• Shown only when the session has history (not a blank chat), is not running, is not a subagent view, and the draft is empty (whitespace counts as empty) with no attachments.
• As soon as the user types or attaches anything, the normal Send button comes back.
• While running, the existing Stop behavior is unchanged.

Why built-in

It can be done as a plugin today, but only awkwardly: conversation.input.right can add a separate button, while the primary Send button itself is not a slot. To make Send become Continue, my local plugin has to find the *_primary button in the DOM, hide it, and portal a replacement into its row. That relies on a hashed CSS class name and will break silently on UI updates.

Minimal ask (either is fine)

1. Built-in: an idle-empty-draft "Continue" state for the primary button (opt-in setting is fine), or
2. Extension point: make the primary action overridable via a slot (e.g. conversation.input.primary), so plugins can do this cleanly.

Tested locally on 0.2.0-rc.2 (desktop) with useSession / useInput / inputActions.setDraft + submit from the slot props; the logic is ~40 lines.

Related: #3303 and #1166 (turns ending on max-tokens wait for a manual "continue").