Use cargo xtask commands in the unsafe deep dive setup page

[ZainnQureshii]

The "(Optional) Create a local instance of the course" block in the Unsafe deep dive setup page (src/unsafe-deep-dive/setup.md) uses cargo install-tools and cargo serve. Those cargo aliases were removed in #2847: .cargo/config.toml now defines only xtask, so both commands fail with "no such command".

Changes:

• cargo install-tools -> cargo xtask install-tools
• cargo serve -> cargo xtask serve

These match the README's Setup and Commands sections (README.md:75, README.md:87-88) and the InstallTools and Serve subcommands in xtask/src/main.rs.

• One sentence pointing to the README's Setup prerequisites. install-tools runs bazel build (xtask/src/main.rs:153), and this page's own Bazel note is inside an HTML comment, so a learner without Bazel would still fail at that step.

Ran in a clone of main (stable Rust):

$ cargo install-tools
error: no such command: `install-tools`
$ cargo serve
error: no such command: `serve`
$ cargo xtask --help
  ...
  install-tools      Installs the tools the project depends on
  ...
  serve              Starts a web server with the course

dprint check passes on the page. The full install-tools and serve runs (Bazel build) were not done.

Prepared with AI assistance (Claude Code) and reviewed with GitHub Copilot.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request updates the setup instructions in src/unsafe-deep-dive/setup.md to correctly use 'cargo xtask install-tools' and 'cargo xtask serve' instead of 'cargo install-tools' and 'cargo serve'. It also adds a note indicating that 'cargo xtask install-tools' requires the prerequisites listed in the repository's README, including Bazel. I have no feedback to provide.