Plan mode: approving a plan should not auto-trigger coding

Problem

When using plan mode for reflection/strategy sessions (not intended to code right away), approving a plan automatically triggers the assistant to start coding. There's no way to approve a plan without entering execution mode.

Steps to reproduce

1. User explicitly says "we're not coding today, just planning"
2. Assistant enters plan mode, writes a plan
3. Assistant calls ExitPlanMode, user approves the plan
4. System message says: "User has approved your plan. You can now start coding."
5. Assistant starts coding immediately, ignoring the user's earlier instruction

Expected behavior

There should be a way to approve a plan without triggering execution. Two options:

• Option A: Add a "Save plan for later" vs "Approve and execute" choice when the plan is presented for approval
• Option B: The assistant should respect explicit user instructions ("don't code today") even after plan approval, and not treat approval as a coding trigger

Context

This is a common workflow for users who do strategy/reflection sessions separate from coding sessions. Plan mode is useful for structuring thoughts, but the automatic transition to coding makes it unusable for planning-only sessions.

Current workaround

Don't use plan mode for reflection sessions — just discuss in normal mode.