style: naming convention with kind and scope prefixes, checked by clang-tidy

.agents/instructions/style/cpp.md

@@ -10,7 +10,8 @@ truth: never edit them to make code pass.
   `else` on its own line. Never a one-line `if`, loop, block or function.
 - Pointer and reference sign bind to the name: `const char *name`.
 - Namespaces `aether::<module>`, closed with `}  // namespace aether::<module>`.
-- Functions and methods are `camelCase`; constants are `kPascalCase`.
+- Names follow `docs/naming.md` (kind and scope prefixes), checked by
+  clang-tidy; the boolean `b` prefix is checked in review.
 - Public headers live under `include/aether/<module>/` and are included with
   angle brackets: `#include <aether/core/version.hpp>`. The module's own
   header comes first, then the others, sorted by clang-format.

.clang-tidy

@@ -8,7 +8,46 @@ Checks: >
   cppcoreguidelines-*,
   bugprone-*,
   clang-analyzer-*,
+  readability-identifier-naming,
   -modernize-use-trailing-return-type
 WarningsAsErrors: false
 HeaderFilterRegex: "(^|/)sources/.+\\.hpp$"
 FormatStyle: Google
+CheckOptions:
+  readability-identifier-naming.NamespaceCase: lower_case
+  readability-identifier-naming.ClassCase: CamelCase
+  readability-identifier-naming.StructCase: CamelCase
+  readability-identifier-naming.AbstractClassCase: CamelCase
+  readability-identifier-naming.AbstractClassPrefix: I
+  readability-identifier-naming.EnumCase: CamelCase
+  readability-identifier-naming.EnumPrefix: E
+  readability-identifier-naming.EnumConstantCase: CamelCase
+  readability-identifier-naming.TypeAliasCase: CamelCase
+  readability-identifier-naming.TypeAliasIgnoredRegexp: "^([iuf][0-9]+|usize)$"
+  readability-identifier-naming.TypedefCase: CamelCase
+  readability-identifier-naming.TypeTemplateParameterCase: CamelCase
+  readability-identifier-naming.TypeTemplateParameterPrefix: T
+  readability-identifier-naming.TypeTemplateParameterIgnoredRegexp: "^T$"
+  readability-identifier-naming.ValueTemplateParameterCase: CamelCase
+  readability-identifier-naming.FunctionCase: camelBack
+  readability-identifier-naming.MethodCase: camelBack
+  readability-identifier-naming.ParameterCase: camelBack
+  readability-identifier-naming.VariableCase: camelBack
+  readability-identifier-naming.LocalVariableCase: camelBack
+  readability-identifier-naming.PublicMemberCase: camelBack
+  readability-identifier-naming.PrivateMemberCase: camelBack
+  readability-identifier-naming.PrivateMemberPrefix: m_
+  readability-identifier-naming.ProtectedMemberCase: camelBack
+  readability-identifier-naming.ProtectedMemberPrefix: m_
+  readability-identifier-naming.ClassMemberCase: camelBack
+  readability-identifier-naming.ClassMemberPrefix: s_
+  readability-identifier-naming.GlobalVariableCase: camelBack
+  readability-identifier-naming.GlobalVariablePrefix: g_
+  readability-identifier-naming.ConstexprVariableCase: CamelCase
+  readability-identifier-naming.ConstexprVariablePrefix: k
+  readability-identifier-naming.GlobalConstantCase: CamelCase
+  readability-identifier-naming.GlobalConstantPrefix: k
+  readability-identifier-naming.StaticConstantCase: CamelCase
+  readability-identifier-naming.StaticConstantPrefix: k
+  readability-identifier-naming.MacroDefinitionCase: UPPER_CASE
+  readability-identifier-naming.MacroDefinitionPrefix: AETHER_

docs/naming.md

@@ -0,0 +1,37 @@
+# Naming
+
+How names are written in the engine. Read it to recognise what a name is in
+the API, or before writing engine code. A name tells its kind and its scope,
+so a diff reads right even without an IDE (a review on GitHub, on a phone).
+
+| Element | Convention | Example |
+| --- | --- | --- |
+| Class, struct, type alias | `PascalCase` | `Texture`, `LogRecord` |
+| Interface (abstract class) | `I` + `PascalCase` | `ISink` |
+| Enum | `E` + `PascalCase` | `ESeverity` |
+| Enum value | `PascalCase` | `ESeverity::Warning` |
+| Type template parameter | `T` + `PascalCase` | `TValue`, `TArgs` |
+| Function, method | `camelCase` | `loadTexture` |
+| Local variable, parameter | `camelCase` | `frameCount` |
+| Public member of a struct | `camelCase` | `record.message` |
+| Private or protected member | `m_` + `camelCase` | `m_file` |
+| Static member | `s_` + `camelCase` | `s_instance` |
+| Global variable | `g_` + `camelCase` | `g_dispatcher` |
+| Constant, `constexpr` | `k` + `PascalCase` | `kMaxLights` |
+| Boolean | `b` + `PascalCase` | `bVisible`, `m_bDirty` |
+| Macro | `AETHER_` + `UPPER_CASE` | `AETHER_ASSERT` |
+| Namespace | `lower_case` | `aether::core` |
+
+How to read it:
+
+- An uppercase prefix marks a type (`E`, `I`, `T`), a lowercase one a value
+  (`m`, `s`, `g`, `k`, `b`).
+- A scope prefix (`m` member, `s` static, `g` global) is followed by `_`,
+  because the name after it starts in lowercase. A type or kind prefix is
+  glued to a capital letter: `ESeverity`, `kMaxLights`, `bVisible`.
+- Prefixes combine, scope first: `m_bDirty`.
+- The fixed-size aliases of `<aether/core/types.hpp>` (`i32`, `u8`, `f32`,
+  `usize`) are lowercase on purpose, like built-in types.
+
+clang-tidy (`readability-identifier-naming` in `.clang-tidy`) checks every
+rule except the boolean one, which is left to review.