Add inline ghost-text autocomplete to text input

[AlexSkrypnyk]

Summary

Add inline ghost-text completion to text input: a dimmed best-match completion after the caret, accepted with Tab or Right-arrow.

Details

This is a distinct interaction from the list-based suggest widget. As the user types, show the single best-matching completion in a dimmed style inline after the caret; Tab or Right-arrow accepts it. Completions come from a static list or a closure over prior answers. Ghost-text keeps the eye on the input line rather than a dropdown.

Acceptance criteria

• Text input can be given a completion source (a static list or a closure over prior answers).
• The best match renders inline after the caret in a dimmed style; Tab/Right accepts it, other keys ignore it.
• With no match, input behaves exactly as a plain text field.
• Ghost-text styling is theme-driven and suppressed in no-ANSI mode.
• Headless collection is unaffected; the typed or answered value is used as-is.
• Unit tests cover match, accept, no-match and no-ANSI rendering.
• The feature is documented in the README text section.