Add 'profile' as a status line item

Feature Request

Add a profile item to the configurable TUI status line (tui.status_line in config.toml).

Motivation

When using --profile to switch between different configurations (e.g., different API endpoints, models, or environments), there's no visual indicator inside the TUI showing which profile is active.

The model name in the status line gives an indirect hint, but profiles represent more than just the model — they can imply different providers or environments. Displaying the profile name directly would make this unambiguous.

Current behavior

/statusline supports: model, model+reasoning, context stats, rate limits, git branch, token counters, session ID, directory, and version — but not the active profile.

Proposed behavior

Add a profile status line item that displays the active --profile / -p name (e.g., production, staging). When no profile is specified, it could show default or be hidden.

Use case

We use a shell wrapper that auto-selects profiles based on the working directory. A visible profile indicator in the TUI footer would let users confirm which profile is active at a glance, without relying on the model name as a proxy.