AI textarea with a send button and optional attachment and voice input buttons
With minLines set to 1 the textarea renders as a single-line field: the submit button sits inline on the first line and drops below the input once the text wraps. This mirrors the homepage hero usage.
Submit expands to a labelled pill once `minCharacters` is reached.
Lines shown at rest before auto-grow, including the stacked toolbar row. Set to 1 for a single-line field with the button inline.
Rounded-rectangle submit instead of round/pill.