[BUG] Raw ANSI escape codes shown in prompt header bar instead of being stripped

Description

When Claude Code captures the shell prompt to display in the header/title bar area of the TUI, raw ANSI escape codes are shown as literal text instead of being rendered as colors or stripped out.

Example

The header bar displays:

# liangsu @ machine in ~/project on \033[34mgit\033[0m:\033[36mfeat/my-branch\033[0m \033[31mx\…

Instead of the expected clean text:

# liangsu @ machine in ~/project on git:feat/my-branch x

Environment

• OS: macOS (Darwin 25.4.0)
• Shell: zsh with oh-my-zsh
• Theme: ys (uses %{$fg[blue]%} style color escapes in PROMPT)
• Claude Code: latest CLI version

Expected behavior

The prompt header should either:

1. Strip ANSI escape codes and display clean plain text, or
2. Render the colors properly

Actual behavior

Raw escape sequences like \033[34m, \033[0m, \033[36m, \033[31m are displayed as literal text in the header bar.

Notes

• The terminal itself renders the prompt colors correctly — only the Claude Code TUI header is affected
• This likely affects all oh-my-zsh themes that use color escapes (ys, agnoster, robbyrussell, etc.)
• A simple regex strip of \033\[[0-9;]*m sequences before displaying would fix it