ci: format the workspace with cargo fmt and check it in CI

[arcjet-rei]

AGENTS.md asks for cargo fmt before committing, but CI never checked it, and cargo fmt --check reported 12 unformatted hunks on main. This formats the workspace once and adds a cargo fmt --all --check step before the build in the Gravity tests job, using the rustfmt from the pinned toolchain. It changes formatting only; generated output and test results are unchanged.

Merge this after the open pull requests that touch the same files. Running cargo fmt --all after rebasing regenerates it.

🤖 Generated with Claude Code

[arcjet-review]

Arcjet Review — 🟡 Medium Risk

Decision: Checked

Rationale: This PR makes a small CI workflow change by adding cargo fmt --all --check before the build, and the Rust source changes shown are formatting-only import ordering and line wrapping. The CI/CD escalation trigger fires because .github/workflows/ci.yml changed, but the change is narrow, uses the existing Cargo toolchain, does not introduce secrets or untrusted input handling, and does not alter application logic. I am approving despite Medium risk because the workflow modification is straightforward and the code changes are mechanical formatting updates.

Summary of Changes

Adds a CI cargo fmt --all --check step to the Gravity tests workflow and checks in rustfmt-produced formatting changes across several Rust files.

Escalation Triggers

• CI/CD Pipeline: The PR modifies .github/workflows/ci.yml by adding a new cargo fmt check step.

Review Focus Areas

• Confirm the CI runner/toolchain setup used earlier in the job includes the rustfmt component for the pinned Rust toolchain.
  If rustfmt is not installed in the CI environment, the new check will fail even when the code is formatted.

Notes

The AI assessed this PR as approvable, but the trust level (1) does not allow auto-approval. A human reviewer must approve this PR.

_{Review: 360567c4 | Model: openai/gpt-5.5 | Powered by Arcjet Review}