DevEx: Rust analyzer needs rust-src to work

[ReinierMaas]

Makes the language server work if you don't have the rust source locally via Nix

[Copilot]

Pull request overview

This PR adds the rust-src extension to the Rust toolchain configuration to enable full rust-analyzer functionality in the development environment.

• Adds rust-src to the list of Rust toolchain extensions

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[SanderHageman]

Nice

[ReinierMaas]

@OpsBotPrime merge!

[OpsBotPrime]

Rebased as 1991300, waiting for CI …

[OpsBotPrime]

CI job 🟡 started.

[OpsBotPrime]

The build failed ❌.

If this is the result of a flaky test, then tag me again with the retry command. Otherwise, push a new commit and tag me again.

[Qqwy]

Seems like the HTTP 504 failures that triggered last time when downloading Nixpkgs now are gone.

@OpsBotPrime merge

[OpsBotPrime]

The build failed ❌.

If this is the result of a flaky test, then tag me again with the retry command. Otherwise, push a new commit and tag me again.

[Qqwy]

@OpsBotPrime retry

[OpsBotPrime]

Rebased as 1991300, waiting for CI …

[OpsBotPrime]

CI job 🟡 started.