CLI markdown renderer has broken syntax highlighting in Windows Terminal

When using Claude Code CLI in Windows Terminal, code blocks in responses have broken syntax highlighting where random substrings within words get colored differently.

Example:
In the bash code unset ANTHROPIC_API_KEY, the substring "ROPIC" (in the middle of ANTHROPIC_API_KEY) renders in a different color than the rest of the variable name.

Environment:

• Claude Code CLI (latest version)
• Windows Terminal
• Happens consistently with bash code blocks

Expected behavior:
Variable names like ANTHROPIC_API_KEY should be highlighted as a single token, not have random substrings colored differently.

Actual behavior:
The markdown renderer breaks words at incorrect boundaries, causing partial word highlighting that makes code harder to read.