ci: add lint and format checks

[tetsuo-cpp]

Summary

• Add check-format CMake target that runs clang-format --dry-run --Werror
• Search for versioned clang-format binary (e.g. clang-format-20) on Ubuntu
• Add Ruff lint and format check step for Python code

Test plan

• cmake --build build --target check-format passes locally
• CI pipeline passes on this PR

[tetsuo-cpp]

Code Review

Overview

Small, well-scoped PR that adds two CI steps:

1. A check-format CMake target that verifies C++ files comply with clang-format (dry-run with --Werror)
2. A Ruff lint + format check step for the Python code in gpu_test/

Also fixes the clang-format binary lookup on Ubuntu by searching for the versioned name (e.g. clang-format-20) first.

Analysis

Correctness — looks good overall.

• clang-format binary search order (CMakeLists.txt): Searching for clang-format-${LLVM_VERSION_MAJOR} before clang-format is the right call for Ubuntu where apt installs versioned binaries. Ensures the format check uses the same LLVM version as the build, avoiding style drift.

• CI step ordering (ci.yml): Format and lint checks run after build and test. This means a formatting-only failure still requires a full build cycle to surface. Consider moving these checks earlier or into a separate lightweight job — it doesn't need MLIR installed, so it could run on a bare image with just clang-format and uv. This would be faster and give clearer signal.

• check-format target has no clang-format fallback (CMakeLists.txt): If clang-format isn't found, both format and check-format are silently unavailable. The CI step would then fail with a confusing "no rule to make target" error. Consider either:

  • Adding a message(WARNING ...) when clang-format isn't found, or
  • Explicitly installing clang-format-20 in the CI apt step to make the dependency explicit rather than relying on it being pulled in transitively by llvm-20-dev.

• Ruff step: Using && to chain ruff check and ruff format --check is fine — if lint fails, format won't run, which is reasonable.

Suggestions

1. Consider a separate CI job for lint/format — doesn't need MLIR, would be much faster and gives independent signal.
2. Install clang-format explicitly in CI — add clang-format-${LLVM_VERSION} to the apt-get install line.
3. Minor: file(GLOB_RECURSE ...) already recurses, so ** in the glob paths is redundant (though harmless).

Verdict

Clean, minimal PR that adds useful CI guardrails. Main suggestion is a separate faster job for lint checks. Otherwise, LGTM.