Plan mode allows rejection after plan was already accepted

Bug Description

After accepting a plan in Plan Mode (selecting an option from the feedback prompt), I was still able to reject/cancel the plan afterward.

Steps to Reproduce

1. Enter plan mode and generate a plan
2. The feedback prompt appears with options (e.g., "Looks good, proceed", "Skip backend prompt", etc.)
3. Accept/select an option from the feedback prompt
4. After acceptance, the plan could still be rejected

Expected Behavior

Once a plan is accepted and an option is selected, it should proceed to implementation without allowing the decision to be reversed.

Screenshot

!Plan mode feedback prompt

(Feedback prompt showing options after plan was already accepted)

Environment

• Claude Code CLI
• Linux