feat(ci): integrate clang-tidy for changed C/C++ files

[kgeg401]

Summary

• add repository-level .clang-tidy with a minimal enforceable check set
• add .github/workflows/clang_tidy.yml to run on C/C++ and CMake-related changes
• configure CMake to export compile_commands.json and run clang-tidy on changed C/C++ files only
• fail CI for clang-tidy findings via --warnings-as-errors='*'

Notes

• workflow still runs configure on CMake changes even when no C/C++ file changed
• .gitignore is updated to allow tracking .clang-tidy

Fixes #74

[kgeg401]

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