[BUG] Input buffer cleared when accepting plan and clearing context in plan mode

Summary

When exiting plan mode by accepting a plan and clearing context, any text staged in the prompt bar (input buffer) is also cleared. This causes loss of user input that was being prepared for the next message.

Steps to Reproduce

1. Enter plan mode (Claude proposes a plan)
2. While reviewing the plan, type some text in the prompt bar as a "buffer" for your next instruction
3. Accept the plan and select "Clear context"
4. Observe that the prompt bar is now empty - the staged text is gone

Expected Behavior

The input buffer should be preserved when clearing context after accepting a plan. The context clear should only affect conversation history, not the user's pending input.

Actual Behavior

Both the conversation context AND the input buffer are cleared, causing loss of any text the user had staged in the prompt bar.

Use Case

Many users (myself included) use the prompt bar as a buffer to stage the next instruction while Claude is working or while reviewing output. Losing this text is frustrating and disrupts workflow.

Environment

• Claude Code version: 2.1.19
• OS: macOS Darwin 24.6.0

Related Issues

• #18755 - Feature Request: Auto-save input buffer to prevent loss of unsaved prompts
• #17502 - Input buffer cleared on ESC
• #879 - Text input clears when message promoted from queue

This appears to be another instance of the broader input buffer preservation problem.