AI prompt box

Build an interactive UI element: AI prompt box.

What it is: An auto-growing input with a model picker, a thinking animation and a reply that appears word by word.

Behaviour:
- Textarea that grows up to 120px high; Enter sends, Shift+Enter adds a new line.
- Row of model choices (for example Claude, GPT, Gemini) as buttons with role="radio"; the selected one is filled.
- Round send button bottom right, disabled while the field is empty, in the accent colour when active.
- After sending: the question as a bubble on the right, below it "<model> is thinking..." with a shimmering text animation; after about a second the reply appears word by word (about 55 ms per word).
- Use a fixed sample reply, or connect it to my own AI endpoint if there is one.

Requirements:
- Work in this project's stack. If it is React with Tailwind CSS, make a single component without extra packages; otherwise plain HTML, CSS and JavaScript.
- Fully operable with keyboard and touch, with the right aria attributes.
- Respect prefers-reduced-motion: less or no movement.
- Use the colours, fonts and border radii of my project.
- At the end, show me where the component lives and how to use it.
- Put a short credit at the top of the file as a comment: "Based on the AI Toolkit by NinA AI Agency, https://www.nina-ai.nl/en/toolkit/ui/ai-prompt-invoer". Keep it there.