[BUG] TUI hangs while Claude is thinking

Environment

• Platform (select one):
• [x] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.84 (Claude Code)
• Operating System: Windows 11
• Terminal: Windows Terminal

Bug Description

<!-- A clear and concise description of the bug -->

Steps to Reproduce

1. Run a task that requires thinking
2. Intermittently, the progress indicator will hang for a couple of seconds and while it does you won't be able to type anything

Expected Behavior

Use a separate thread for computation and UI input/output. Alternatively, yield() on a regular basis in the computation thread.

Actual Behavior

UI hangs while computation is in progress