Allow users to control which fields appear in the interactive CLI status
bar via display.status_bar.fields in config.yaml.
Available fields: model, context_pct, context_detail, compressions,
bg_tasks, bg_processes, duration, prompt_elapsed, yolo, total_tokens.
When the list is empty (default), all fields are shown as before.
The field order is fixed (model always first); the config controls
visibility only. Narrow terminals (<76 cols) automatically drop
context_detail regardless of config.
total_tokens is opt-in only (not shown by default) to avoid width
overflow in the prompt_toolkit fragment renderer.
Closes#41909
liuhao1024
fb786d2f5b