[BUG] `/clear` command injects non json-lines data in streaming usage

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [x] Other: <!-- specify -->
• Claude CLI version: <!-- output of claude --version -->
• 1.0.89 (Claude Code)

• Operating System: <!-- e.g. macOS 14.3, Windows 11, Ubuntu 22.04 -->

Ubuntu 24.04.2 LTS

• Terminal: <!-- e.g. iTerm2, Terminal App -->

Bug Description

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When running claude code in json streaming mode (SDK styled usage), if you issue the /clear command, some non-json data will get injected into the standard output (\^[[2J\^[[3J\^[[H) Perhaps intended to clear the screen in interactive mode?

Steps to Reproduce

1. <!-- First step -->
2. <!-- Second step -->
3. <!-- And so on... -->

Expected Behavior

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Actual Behavior

<!-- What actually happened -->

Additional Context

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