Add ai-ui (a Rust port of assistant-ui: chat runtime, AI SDK streaming, Markdown, an optional Slint chat UI) to this project.

1. Get the skill: download https://iyiolacak.github.io/ai-ui-rewrite-rust/skill/ai-ui/SKILL.md and every reference file it links into .claude/skills/ai-ui/, keeping the same relative paths. If you can't write there, read them from those URLs instead.
2. Follow the skill. Inspect this project first, then tell me what you found and which crates you plan to add before changing anything.
3. Then do the work: add the crates, wire them up, and finish with cargo build, cargo clippy -- -D warnings, cargo test and one message actually sent and streamed back. Report what you changed, what you ran, and anything you couldn't verify.