[BUG] Arrow Key Navigation Broken When Using Multiple Pasted Text Blocks

Environment

• Platform (select one):
• [ ] Anthropic API
• [X] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.22 (Claude Code)<!-- output of claude --version -->
• Operating System: MacOS 15.5 (24F74) <!-- e.g. macOS 14.3, Windows 11, Ubuntu 22.04 -->
• Terminal: Iterm2 <!-- e.g. iTerm2, Terminal App -->

Bug Description

When entering a multiline message with pasted text blocks, the up arrow key navigation doesn't work properly. Instead of navigating to previous lines within the current message, pressing the up arrow jumps to the previous chat message.
<!-- A clear and concise description of the bug -->

Steps to Reproduce

1. Open a Claude session with existing chat history
2. Paste a text block
3. Press Enter to create a new line
4. Paste another text block
5. Press Enter again to create an empty line
6. Add some text on the new line
7. Press the up arrow key

Expected Behavior

When pressing the up arrow key, it should navigate to the previous line within the current message (empty line → second pasted block → first pasted block), allowing in-message navigation.

Actual Behavior

<!-- What actually happened -->
When pressing the up arrow key, instead of navigating to the previous lines within the current message, it jumps to the previous chat message entirely, skipping over the pasted text blocks as if they were not navigable content.

Additional Context

<!-- Add any other context about the problem here, such as screenshots, logs, etc. -->
https://github.com/user-attachments/assets/ffb51318-353c-4b2d-8b01-085f6b73df8d