Document clang-tidy exclusions and drop unneeded ones

Re-enable every excluded check in a run of clang-tidy 22 over all tests
and remove the seven that never fire (cert-err58-cpp,
clang-analyzer-webkit.NoUncountedMemberChecker,
cppcoreguidelines-virtual-class-destructor, google-readability-function-size,
hicpp-function-size, hicpp-no-assembler, readability-function-size).

Document the reason for every remaining exclusion at the top of the file.

Exclude in advance the checks that only exist in clang-tidy 23 and are
noise here (bugprone-signed-bitwise, *-explicit-constructor,
readability-trailing-comma, modernize-use-string-view), plus
modernize-use-integer-sign-comparison, which needs C++20 std::cmp_less
and flags deliberate casts.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

.clang-tidy

@@ -1,3 +1,33 @@
+# Style or vendor rule sets that do not fit a header-only library:
+#   altera-*, fuchsia-*, llvmlibc-*, android-cloexec-fopen, boost-use-ranges, llvm-header-guard,
+#   llvm-include-order, llvm-prefer-static-over-anonymous-namespace, llvm-use-ranges,
+#   misc-use-anonymous-namespace, google-runtime-float, google-runtime-int, hicpp-signed-bitwise,
+#   bugprone-signed-bitwise, hicpp-explicit-conversions, google-explicit-constructor,
+#   cppcoreguidelines-explicit-constructor, misc-explicit-constructor (implicit conversions are the
+#   API), readability-trailing-comma,
+#   hicpp-avoid-goto / cppcoreguidelines-avoid-goto, hicpp-no-array-decay,
+#   hicpp-uppercase-literal-suffix, readability-uppercase-literal-suffix, modernize-use-trailing-return-type.
+# Constructs the library needs on purpose (the library supports C++11 and legacy compilers):
+#   cppcoreguidelines-macro-usage, cppcoreguidelines-avoid-do-while (macros),
+#   cppcoreguidelines-pro-bounds-*, cppcoreguidelines-pro-type-reinterpret-cast,
+#   cppcoreguidelines-pro-type-union-access (parsers, serializers, basic_json's value union),
+#   cppcoreguidelines-avoid-const-or-ref-data-members, cppcoreguidelines-rvalue-reference-param-not-moved,
+#   cppcoreguidelines-avoid-non-const-global-variables, misc-non-private-member-variables-in-classes,
+#   misc-no-recursion (value walks are recursive, bounded by detail::recursion_depth_limit()),
+#   modernize-type-traits, modernize-use-constraints, modernize-use-ranges, modernize-use-std-numbers,
+#   modernize-use-designated-initializers, modernize-use-nodiscard, modernize-concat-nested-namespaces,
+#   readability-redundant-typename, readability-redundant-parentheses,
+#   readability-redundant-access-specifiers, readability-simplify-boolean-expr,
+#   readability-use-concise-preprocessor-directives, modernize-use-string-view,
+#   modernize-use-integer-sign-comparison (needs std::cmp_less; the flagged
+#   static_cast<std::size_t>(end - pos) < n comparisons are deliberate)
+#   (all need a newer standard or compiler than C++11, or would change macro-generated or
+#   deliberately explicit code).
+# Too noisy to be useful (numeric parsing/formatting code, doctest, tests):
+#   bugprone-easily-swappable-parameters, cppcoreguidelines-avoid-magic-numbers, readability-magic-numbers,
+#   readability-identifier-length, readability-function-cognitive-complexity, performance-enum-size,
+#   concurrency-mt-unsafe, misc-confusable-identifiers, misc-include-cleaner (run on its own for
+#   the consumer headers in cmake/ci.cmake).
 # portability-avoid-pragma-once: kept disabled on purpose. #pragma once is accepted
 # by every supported compiler, and tools/amalgamate/amalgamate.py strips it from
 # single_include, so there is nothing left to fix here.
@@ -10,14 +40,14 @@ Checks: '*,
          -android-cloexec-fopen,
          -boost-use-ranges,
          -bugprone-easily-swappable-parameters,
-         -cert-err58-cpp,
-         -clang-analyzer-webkit.NoUncountedMemberChecker,
+         -bugprone-signed-bitwise,
          -concurrency-mt-unsafe,
          -cppcoreguidelines-avoid-const-or-ref-data-members,
          -cppcoreguidelines-avoid-do-while,
          -cppcoreguidelines-avoid-goto,
          -cppcoreguidelines-avoid-magic-numbers,
          -cppcoreguidelines-avoid-non-const-global-variables,
+         -cppcoreguidelines-explicit-constructor,
          -cppcoreguidelines-macro-usage,
          -cppcoreguidelines-pro-bounds-avoid-unchecked-container-access,
          -cppcoreguidelines-pro-bounds-array-to-pointer-decay,
@@ -26,19 +56,15 @@ Checks: '*,
          -cppcoreguidelines-pro-type-reinterpret-cast,
          -cppcoreguidelines-pro-type-union-access,
          -cppcoreguidelines-rvalue-reference-param-not-moved,
-         -cppcoreguidelines-virtual-class-destructor,
          -fuchsia-default-arguments-calls,
          -fuchsia-default-arguments-declarations,
          -fuchsia-overloaded-operator,
          -google-explicit-constructor,
-         -google-readability-function-size,
          -google-runtime-float,
          -google-runtime-int,
          -hicpp-avoid-goto,
          -hicpp-explicit-conversions,
-         -hicpp-function-size,
          -hicpp-no-array-decay,
-         -hicpp-no-assembler,
          -hicpp-signed-bitwise,
          -hicpp-uppercase-literal-suffix,
          -llvm-header-guard,
@@ -48,6 +74,7 @@ Checks: '*,
          -llvmlibc-*,
          -misc-use-anonymous-namespace,
          -misc-confusable-identifiers,
+         -misc-explicit-constructor,
          -misc-include-cleaner,
          -misc-no-recursion,
          -misc-non-private-member-variables-in-classes,
@@ -55,20 +82,22 @@ Checks: '*,
          -modernize-type-traits,
          -modernize-use-constraints,
          -modernize-use-designated-initializers,
+         -modernize-use-integer-sign-comparison,
          -modernize-use-nodiscard,
          -modernize-use-ranges,
+         -modernize-use-string-view,
          -modernize-use-std-numbers,
          -modernize-use-trailing-return-type,
          -performance-enum-size,
          -portability-avoid-pragma-once,
          -readability-function-cognitive-complexity,
-         -readability-function-size,
          -readability-identifier-length,
          -readability-magic-numbers,
          -readability-redundant-access-specifiers,
          -readability-redundant-parentheses,
          -readability-redundant-typename,
          -readability-simplify-boolean-expr,
+         -readability-trailing-comma,
          -readability-uppercase-literal-suffix,
          -readability-use-concise-preprocessor-directives'