Session name chip in statusline has no background color (plain text only)

Description

The session name displayed in the bottom statusline no longer renders as a highlighted chip with a background color. It shows as plain, unstyled text against the terminal background, making it unreadable depending on the terminal color scheme.

Steps to reproduce

1. Open macOS Terminal.app
2. Start a new Claude Code session
3. Run /rename <name> or observe the default session name
4. Look at the bottom-right of the statusline

Expected behavior

The session name renders as a colored chip with a background color (previously teal/cyan) and contrasting text.

Actual behavior

The session name renders as plain text with no background color, against whatever the terminal background is.

Additional notes

• Changing the theme via /config applies colors to other UI elements but does not restore the chip background on the session name label.
• The issue is present in fresh sessions, not just renamed ones.
• Previously worked correctly; regression appeared around v2.1.280.

Environment

• Claude Code version: 2.1.282
• OS: macOS
• Terminal: macOS Terminal.app
• Theme setting: light-daltonized