Feature request: toggle for automatic Plan/Implement mode switching

Feature request

Add a user-controlled toggle that lets Codex automatically switch between Plan mode and Implement mode during its own workflow, then switch back when appropriate.

Problem

For larger tasks, Codex often needs to move through a natural loop: plan, ask or resolve blockers, implement, test, summarize, then return to planning if a new decision or blocker appears. When mode switching is manual, the user has to manage that workflow state explicitly, which interrupts momentum and makes the agent feel less continuous.

Proposed behavior

Introduce a toggle such as Allow automatic Plan/Implement switching. When enabled:

• Codex can move from Plan mode to Implement mode once the necessary decisions, constraints, or approvals are satisfied.
• Codex can return from Implement mode to Plan mode after completing implementation, hitting a blocker, finishing verification, or needing a new user decision.
• Codex should announce each mode switch and briefly explain why it is switching.
• The toggle should be easy to disable, preferably scoped per thread, workspace, or session.
• Existing approval, sandbox, and permission settings should remain authoritative.

Why this helps

This would reduce manual coordination for multi-step engineering work while preserving user control. It would let Codex manage its own planning/implementation loop more naturally without requiring the user to repeatedly switch modes by hand.