chore(scripts): add local clang-format diff-gate helper

[virtexalejandro]

Local mirror of the CI clang-format diff-gate so developers can validate their changed lines before pushing.

Tools shipped

• scripts/check_clang_format.py -- actual logic, Python.
• scripts/check_clang_format.sh / .bat -- thin wrappers (Linux/macOS/WSL/Git Bash + Windows cmd).
• scripts/git-hooks/pre-push -- versioned git hook that calls the check before every push.

Usage

python scripts/check_clang_format.py        # check vs origin/main
python scripts/check_clang_format.py --fix  # apply fixes in place
python scripts/check_clang_format.py --base HEAD~1  # different base ref

Opt in to the pre-push hook (one-time per clone)

git config core.hooksPath scripts/git-hooks

That points git at the versioned hooks directory in the repo. No external dependency (Husky, pre-commit, etc.) -- just core.hooksPath, which is built into git ≥ 2.9.

To bypass the hook for a one-off push:

git push --no-verify

To disable entirely in your clone:

git config --unset core.hooksPath

What the check does

Same exact logic as the existing CI clang-format job (.github/workflows/build.yml):

• Diff-gate: only validates lines modified vs a base ref, not whole files.
• Same exclusions: thirdparty/, *generated/, arena_generated.h, portable-file-dialogs.h.
• Same scope: .cpp, .cc, .h, .hpp.
• Same flags: -p1 -style=file.

Exit codes

• 0 clean (or nothing in scope)
• 1 violations found (CI would fail here)
• 2 tooling missing (clang-format / clang-format-diff)

Cross-platform notes

On Windows, the script auto-detects clang-format-diff.py under Program Files\LLVM\share\clang\ when not on PATH (LLVM installer doesn't add it). On Linux/macOS, clang-format-diff-15 (or any versioned variant) ships with the clang-format package.