CI: Bump clang-format and clang-tidy versions

• clang-format: 20.1.0 → 21.1.7
• clang-tidy: 20.1.0 → 21.1.6
• `.clang-format`: 17.0.6 → 18.1.8 (keep 3 versions behind latest for compatibility)

.pre-commit-config.yaml

@@ -11,7 +11,7 @@ exclude: |
 
 repos:
   - repo: https://github.com/pre-commit/mirrors-clang-format
-    rev: v20.1.0
+    rev: v21.1.7
     hooks:
       - id: clang-format
         files: \.(c|h|cpp|hpp|cc|hh|cxx|hxx|m|mm|inc|java)$
@@ -29,7 +29,7 @@ repos:
         files: \.(c|h|cpp|hpp|cc|hh|cxx|hxx|m|mm|inc|java|glsl)$
         args: [--fix, --quiet, --use-color]
         types_or: [text]
-        additional_dependencies: [clang-tidy==20.1.0]
+        additional_dependencies: [clang-tidy==21.1.6]
         require_serial: true
         stages: [manual] # Not automatically triggered, invoked via `pre-commit run --hook-stage manual clang-tidy`