[BUG] Terminal rendering corruption during AI response generation (Frosting state)

Environment

• Platform: macOS Darwin 25.2.0
• Terminal: iTerm2
• Claude Code Version: Latest
• Plugin: oh-my-claudecode (with HUD statusline)

Description

During AI response generation ("Frosting..." loading state), the terminal rendering becomes corrupted. Text gets truncated, overlapped, and mispositioned.

Screenshots

The issue manifests as:

• Text fragments appearing at wrong positions
• Truncated text ("ard shortcuts for locked" instead of full text)
• Input prompt $ appearing in wrong location
• Status bar text bleeding into main output area

Steps to Reproduce

1. Start Claude Code with a plugin that adds a status line (e.g., oh-my-claudecode HUD)
2. Submit a query that requires tool use / multiple operations
3. While AI is generating response ("Frosting..." state)
4. Observe: Text rendering becomes corrupted intermittently

Expected Behavior

Text should render cleanly without overlap or truncation during all loading states.

Actual Behavior

• Text fragments appear truncated
• Lines overlap with each other
• Cursor/prompt position becomes incorrect
• Rendering artifacts persist until screen refresh

Analysis

This appears to be a race condition in React Ink's rendering during:

1. Concurrent updates (AI streaming + status line updates)
2. Terminal resize/reflow calculations
3. Multiple render regions updating simultaneously

The issue is exacerbated when plugins add additional render regions (like status bars) that compete for terminal space during rapid updates.

Impact

• Severity: Medium - Cosmetic but confusing
• Frequency: Intermittent, more common with plugins
• Workaround: Wait for completion, screen usually corrects itself

Related

• May be related to terminal escape sequence handling
• Similar to IME positioning issues (#18291, #16322) in that Ink rendering assumptions break