Capstone: Typed Todo Engine

Combine classes, Maps, closures, immutable updates, interfaces, unions, and generics into a complete in-memory todo store.

Step 1 of 6

Build a typed in-memory todo store

This capstone exercises everything from the module:

Interface for the Todo shape, with a literal-string union for priority.
Type alias for an optional filter shape using indexed access.
Map as the underlying store for O(1) lookup by id.
Closure to keep the Map private inside createStore.
Immutable updates when toggling a todo (no in-place mutation).
Generic find<K extends keyof Todo> for typesafe lookups by any field.
=== only for comparisons.

Take it one step at a time. Each step builds on the previous one.