feat: add C++ language support and hook tests (#539)

- agents: cpp-build-resolver, cpp-reviewer
- commands: cpp-build, cpp-review, cpp-test
- rules: cpp/ (coding-style, hooks, patterns, security, testing)
- tests: 9 new hook test files with comprehensive coverage

Cherry-picked from PR #436.

rules/cpp/coding-style.md

@@ -0,0 +1,44 @@
+---
+paths:
+  - "**/*.cpp"
+  - "**/*.hpp"
+  - "**/*.cc"
+  - "**/*.hh"
+  - "**/*.cxx"
+  - "**/*.h"
+  - "**/CMakeLists.txt"
+---
+# C++ Coding Style
+
+> This file extends [common/coding-style.md](../common/coding-style.md) with C++ specific content.
+
+## Modern C++ (C++17/20/23)
+
+- Prefer **modern C++ features** over C-style constructs
+- Use `auto` when the type is obvious from context
+- Use `constexpr` for compile-time constants
+- Use structured bindings: `auto [key, value] = map_entry;`
+
+## Resource Management
+
+- **RAII everywhere** — no manual `new`/`delete`
+- Use `std::unique_ptr` for exclusive ownership
+- Use `std::shared_ptr` only when shared ownership is truly needed
+- Use `std::make_unique` / `std::make_shared` over raw `new`
+
+## Naming Conventions
+
+- Types/Classes: `PascalCase`
+- Functions/Methods: `snake_case` or `camelCase` (follow project convention)
+- Constants: `kPascalCase` or `UPPER_SNAKE_CASE`
+- Namespaces: `lowercase`
+- Member variables: `snake_case_` (trailing underscore) or `m_` prefix
+
+## Formatting
+
+- Use **clang-format** — no style debates
+- Run `clang-format -i <file>` before committing
+
+## Reference
+
+See skill: `cpp-coding-standards` for comprehensive C++ coding standards and guidelines.

rules/cpp/hooks.md

@@ -0,0 +1,39 @@
+---
+paths:
+  - "**/*.cpp"
+  - "**/*.hpp"
+  - "**/*.cc"
+  - "**/*.hh"
+  - "**/*.cxx"
+  - "**/*.h"
+  - "**/CMakeLists.txt"
+---
+# C++ Hooks
+
+> This file extends [common/hooks.md](../common/hooks.md) with C++ specific content.
+
+## Build Hooks
+
+Run these checks before committing C++ changes:
+
+```bash
+# Format check
+clang-format --dry-run --Werror src/*.cpp src/*.hpp
+
+# Static analysis
+clang-tidy src/*.cpp -- -std=c++17
+
+# Build
+cmake --build build
+
+# Tests
+ctest --test-dir build --output-on-failure
+```
+
+## Recommended CI Pipeline
+
+1. **clang-format** — formatting check
+2. **clang-tidy** — static analysis
+3. **cppcheck** — additional analysis
+4. **cmake build** — compilation
+5. **ctest** — test execution with sanitizers

rules/cpp/patterns.md

@@ -0,0 +1,51 @@
+---
+paths:
+  - "**/*.cpp"
+  - "**/*.hpp"
+  - "**/*.cc"
+  - "**/*.hh"
+  - "**/*.cxx"
+  - "**/*.h"
+  - "**/CMakeLists.txt"
+---
+# C++ Patterns
+
+> This file extends [common/patterns.md](../common/patterns.md) with C++ specific content.
+
+## RAII (Resource Acquisition Is Initialization)
+
+Tie resource lifetime to object lifetime:
+
+```cpp
+class FileHandle {
+public:
+    explicit FileHandle(const std::string& path) : file_(std::fopen(path.c_str(), "r")) {}
+    ~FileHandle() { if (file_) std::fclose(file_); }
+    FileHandle(const FileHandle&) = delete;
+    FileHandle& operator=(const FileHandle&) = delete;
+private:
+    std::FILE* file_;
+};
+```
+
+## Rule of Five/Zero
+
+- **Rule of Zero**: Prefer classes that need no custom destructor, copy/move constructors, or assignments
+- **Rule of Five**: If you define any of destructor/copy-ctor/copy-assign/move-ctor/move-assign, define all five
+
+## Value Semantics
+
+- Pass small/trivial types by value
+- Pass large types by `const&`
+- Return by value (rely on RVO/NRVO)
+- Use move semantics for sink parameters
+
+## Error Handling
+
+- Use exceptions for exceptional conditions
+- Use `std::optional` for values that may not exist
+- Use `std::expected` (C++23) or result types for expected failures
+
+## Reference
+
+See skill: `cpp-coding-standards` for comprehensive C++ patterns and anti-patterns.

rules/cpp/security.md

@@ -0,0 +1,51 @@
+---
+paths:
+  - "**/*.cpp"
+  - "**/*.hpp"
+  - "**/*.cc"
+  - "**/*.hh"
+  - "**/*.cxx"
+  - "**/*.h"
+  - "**/CMakeLists.txt"
+---
+# C++ Security
+
+> This file extends [common/security.md](../common/security.md) with C++ specific content.
+
+## Memory Safety
+
+- Never use raw `new`/`delete` — use smart pointers
+- Never use C-style arrays — use `std::array` or `std::vector`
+- Never use `malloc`/`free` — use C++ allocation
+- Avoid `reinterpret_cast` unless absolutely necessary
+
+## Buffer Overflows
+
+- Use `std::string` over `char*`
+- Use `.at()` for bounds-checked access when safety matters
+- Never use `strcpy`, `strcat`, `sprintf` — use `std::string` or `fmt::format`
+
+## Undefined Behavior
+
+- Always initialize variables
+- Avoid signed integer overflow
+- Never dereference null or dangling pointers
+- Use sanitizers in CI:
+  ```bash
+  cmake -DCMAKE_CXX_FLAGS="-fsanitize=address,undefined" ..
+  ```
+
+## Static Analysis
+
+- Use **clang-tidy** for automated checks:
+  ```bash
+  clang-tidy --checks='*' src/*.cpp
+  ```
+- Use **cppcheck** for additional analysis:
+  ```bash
+  cppcheck --enable=all src/
+  ```
+
+## Reference
+
+See skill: `cpp-coding-standards` for detailed security guidelines.

rules/cpp/testing.md

@@ -0,0 +1,44 @@
+---
+paths:
+  - "**/*.cpp"
+  - "**/*.hpp"
+  - "**/*.cc"
+  - "**/*.hh"
+  - "**/*.cxx"
+  - "**/*.h"
+  - "**/CMakeLists.txt"
+---
+# C++ Testing
+
+> This file extends [common/testing.md](../common/testing.md) with C++ specific content.
+
+## Framework
+
+Use **GoogleTest** (gtest/gmock) with **CMake/CTest**.
+
+## Running Tests
+
+```bash
+cmake --build build && ctest --test-dir build --output-on-failure
+```
+
+## Coverage
+
+```bash
+cmake -DCMAKE_CXX_FLAGS="--coverage" -DCMAKE_EXE_LINKER_FLAGS="--coverage" ..
+cmake --build .
+ctest --output-on-failure
+lcov --capture --directory . --output-file coverage.info
+```
+
+## Sanitizers
+
+Always run tests with sanitizers in CI:
+
+```bash
+cmake -DCMAKE_CXX_FLAGS="-fsanitize=address,undefined" ..
+```
+
+## Reference
+
+See skill: `cpp-testing` for detailed C++ testing patterns, TDD workflow, and GoogleTest/GMock usage.