[BUG] Diff view gutter indicators render as empty squares (□)

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?

In the VS Code extension's inline diff view, the elements on the left side of modified lines are rendered as empty squares (□) instead of their intended appearance. This has been happening for some time and persists across extension updates, VS Code restarts, and full reinstallations.

What Should Happen?

The gutter indicators next to modified lines should render as proper elements.

Error Messages/Logs

Using VS Code Developer Tools (Help → Toggle Developer Tools → Console), the following error was found:
Loading the font 'data:font/ttf;base64,...' violates the following Content Security Policy directive: "font-src 'self' https://.vscode-cdn.net". The action has been blocked.

Steps to Reproduce

1. Open a project in VS Code with the Claude Code extension
2. Ask Claude to edit a file in "Ask before edits" mode
3. Observe the diff view that appears in the chat panel
4. Notice that the gutter indicators to the left of the red/green diff lines appear as empty square characters (□) instead of proper UI elements

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.69

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

_No response_