Implement code improvements using GitHub Copilot tools: Review

Typing `/fix` into Copilot's inline chat inside a messy `Trie.cs` file is what this module is all about. Everything before that final exercise is just a long-winded product tour of features you've probably already found by accident. The sandbox is nice—no local setup, it just works—but you'll need your own Copilot subscription active to actually run the commands.

The module walks you through using the inline chat to add comments, `/explain` to figure out what the original dev was thinking, and then that `/fix` command to patch up some obvious performance holes. It's a decent demo. It shows how to use the chat view to suggest refactoring into separate classes, which is something I'd normally just do myself, but seeing Copilot's take is interesting. It even has you generate unit tests with `/tests`, which is probably the most useful bit for my own workflow. I spend too much time writing boilerplate for tests.

But let's be real. The code is simple. This isn't stress-testing Copilot. It's giving it a softball pitch. The refactoring suggestions are standard, textbook stuff. If you're a senior dev, you're not learning new refactoring techniques here. You're learning the buttons to push to make the robot do the refactoring you were already going to do. And honestly, that's fine. It's a tool. This module teaches you how to hold it.