Add built-in preset options for status line configuration

What would you like to be added?

Add a built-in interactive status line configuration flow that lets users choose from common status line items with a multi-select UI.

For example, users could run /statusline and select items such as:

• Theme colors
• Current model
• Model with reasoning level
• Current working directory
• Project name
• Git branch
• Pull request number
• Context usage / token usage

The flow should show a live preview of the resulting status line while users toggle options, then write the generated configuration after confirmation.

This should complement, not replace, the current dynamic setup path. Users who want a custom shell-command based status line should still be able to use the existing agent-assisted setup and manual ui.statusLine configuration.

Why is this needed?

The current status line feature is powerful, but setup requires either:

1. asking the /statusline setup agent to generate a command, or
2. manually writing a shell command in settings.json.

That flexibility is useful for advanced customization, but it can make the first-time experience feel heavier than necessary for common cases.

Codex provides a simpler reference point: its status line setup presents common display items as built-in options that users can toggle directly. This makes the configuration path clearer and more discoverable, especially for users who only want standard information such as project name, branch, model, or PR number.

Adding preset options would improve the default UX while preserving the escape hatch for advanced users.

Additional context

Current Qwen Code behavior:

• /statusline launches a setup agent.
• ui.statusLine currently supports a shell command config: { "type": "command", "command": "..." }.
• The command receives structured JSON context via stdin and can render arbitrary output.

Suggested product direction:

• Keep the existing dynamic command-based configuration.
• Add a simpler preset-based configuration path for common status line items.
• Consider exposing it through the same /statusline command, with choices such as:
  • "Use built-in presets"
  • "Generate a custom status line with the setup agent"
  • "Edit manually"
• The preset flow should be interactive, searchable, and show selected/unselected states plus a preview, similar to the attached Codex example.