[BUG] Input renderer strips duplicate $ signs when pasting multi-line text

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

$$ (two consecutive dollar signs) gets reduced to a single $ when pasting multi-line text.
When pasting multi-line text into the Claude Code input field, it collapses into a summary preview showing the line count. During this conversion, any $$ in the pasted text loses a $. Pasting a single line or just $$ by itself preserves it correctly.

What Should Happen?

$$ preserved as-is in all paste scenarios

Error Messages/Logs

Steps to Reproduce

1. Copy multiple lines of text containing $$
2. Paste into Claude Code input field
3. The input collapses into a line-count summary preview
4. $$ in the pasted text becomes $

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.42 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_