[Bug] Input Freeze on Startup with @-Import Syntax in CLAUDE.md

Bug Description
[BUG] CLAUDE.md @-import syntax causes complete input freeze on startup (v2.0.5 regression)

Environment

• Claude Code Version: v2.0.5
• OS: Windows 11
• Terminal: Windows Terminal
• Shell: Nushell
• Previously Working Version: v1.x (imports worked before v2.0)

What's Wrong?

When CLAUDE.md contains ANY file import using the documented @path/to/file syntax, Claude Code becomes completely unresponsive
to keyboard input on startup. The interface appears to work (statusline updates, IDE integration shows selections) but no
typing is possible.

Symptoms:

• Cannot type anything in the input prompt
• UI remains responsive (shows statusline updates, IDE integration)
• Only workaround: Paste multiline text using Ctrl+V temporarily restores input capability
• Pasting single-line text does NOT work

What Should Happen?

According to the https://github.com/anthropics/claude-code/blob/main/CHANGELOG.md#0-2-107, CLAUDE.md files should support
importing other files using @path/to/file.md syntax:

0.2.107: CLAUDE.md files can now import This is a v2.0.x regression. The @path/to/file import syntax worked correctly in v1.x versions without causing input freezes.

Additional Context

• The freeze happens consistently on every startup when unescaped @-mentions are present
• The issue affects ANY file path with @ prefix, not just specific files
• Escaping with code spans (backticks) prevents the processing and resolves the freeze
• This suggests the @-import parser may be running synchronously and blocking the input event loop

Expected Behavior

Either:

1. Only process @imports when they appear at the start of a line (not mid-sentence)
2. Require explicit syntax like front-of-line position or special formatting
3. Add documentation about escaping @-mentions in regular text with backticks
4. Make @-import parsing non-blocking/asynchronous to prevent input freezes

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.0.5
• Feedback ID: 63de00c0-37fd-4bac-b581-ae592a1806dc

Errors

[{"error":"Error: Request was aborted.\n    at new W5 (unknown:1:28)\n    at new _Y (B:/~BUN/root/claude.exe:732:18247)\n    at new $2 (B:/~BUN/root/claude.exe:732:19033)\n    at makeRequest (B:/~BUN/root/claude.exe:871:3864)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-10-03T17:12:21.153Z"}]