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/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