Build a todo app

Time to combine everything: signals, events, lists, and conditional classes. You will build a working todo list.

# The features

• Add a todo from the input.
• Toggle a todo's done state by clicking its text.
• Delete a todo with a button.
• Count how many todos are incomplete.

# Hints

• Use ${() => repeat(todos.value, (t) => t.id, (t) => html\...`)}` for the list.
• Toggle: todos.value = todos.value.map(t => t.id === id ? { ...t, done: !t.done } : t).
• Delete: todos.value = todos.value.filter(t => t.id !== id).
• Strike-through done items with a done class (the preview CSS already styles .done).

# Your task

Complete the App function. The add helper is already written — wire up the input and add button, then implement toggle, delete, and the remaining count.