Plan mode reuses existing plan file when re-entering — no way to create a new plan

Problem

When re-entering plan mode in the same session, it reassigns the same plan file from the previous planning session. There's no way to create a new plan file while preserving the existing one.

Steps to Reproduce

1. Enter plan mode → creates plan-01.md
2. Write a plan for Task A, exit plan mode, execute
3. Later in the same session, enter plan mode for a different Task B
4. Plan mode assigns the same plan-01.md with the message "this is the only file you are allowed to edit"
5. The only way to write the new plan is to overwrite the old one

Current Behavior

• Re-entering plan mode reuses the existing plan file
• System message says the existing file is "the only file you are allowed to edit"
• No option to create a fresh plan file
• Workaround: exit plan mode entirely and write the plan to a regular file, losing plan mode benefits

Additional Issue: ExitPlanMode rejection contradiction

During the same session, ExitPlanMode was rejected multiple times with "the user doesn't want to proceed" while the system reminder simultaneously said "Exited Plan Mode." This created a confusing state where it was unclear whether plan mode was active or not.

Expected Behavior

• Re-entering plan mode should create a new plan file (plan-02.md) rather than reassigning the existing one
• OR there should be a way to specify "create new plan" vs "continue existing plan" when entering plan mode
• ExitPlanMode rejection messages should not contradict the system state

Environment

• Claude Code CLI
• Model: Opus 4.6
• macOS Darwin 25.2.0