Fix nix build command

[sequencer]

• Fix Nix build failure caused by missing scala3-sbt-bridge:3.7.3 dependency
• Add bindgen/compile to depsWarmupCommand to fetch Scala 3.7.3 compiler bridge during dependency phase

[Copilot]

Pull request overview

This PR fixes a Nix build failure caused by a missing scala3-sbt-bridge:3.7.3 dependency by adding the bindgen/compile command to the dependency warmup phase and updating the dependency hash accordingly. It also adds CI validation to ensure future Nix builds remain functional.

• Adds bindgen/compile to depsWarmupCommand in flake.nix to fetch the Scala 3.7.3 compiler bridge during the dependency phase
• Updates depsSha256 hash to reflect the new dependency set
• Introduces a new nix_build CI job to validate Nix builds and prevent future regressions

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
flake.nix	Adds bindgen/compile to dependency warmup commands and updates dependency hash to include Scala 3.7.3 compiler bridge
.github/workflows/ci.yml	Adds new nix_build CI job to validate Nix builds and integrates it into the Mergify checkpoint

---

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