docs: Add CLAUDE.md project context file

- Build & test commands
- Architecture overview
- Thread safety patterns (scoped_lock, shared_mutex)
- ModuleLoader usage guidelines
- Known issues and debugging tools

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

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+# GroveEngine - Claude Code Context
+
+## Project Overview
+GroveEngine is a C++17 hot-reload module system for game engines. It supports dynamic loading/unloading of modules (.so) with state preservation during hot-reload.
+
+## Build & Test
+```bash
+# Build
+cmake -B build && cmake --build build -j4
+
+# Run all tests (23 tests)
+cd build && ctest --output-on-failure
+
+# Build with ThreadSanitizer
+cmake -DGROVE_ENABLE_TSAN=ON -B build-tsan
+cmake --build build-tsan -j4
+```
+
+## Architecture
+
+### Key Components
+- **ModuleLoader**: Handles dlopen/dlclose of .so modules with hot-reload support
+- **SequentialModuleSystem**: Single-threaded module execution for testing
+- **IntraIOManager**: Inter-module communication with pub/sub routing
+- **TopicTree**: O(k) topic matching with wildcard support
+
+### Thread Safety Patterns
+See `docs/coding_guidelines.md` for detailed synchronization guidelines.
+
+**DO:**
+```cpp
+// Multiple mutexes - use scoped_lock (deadlock-free)
+std::scoped_lock lock(mutex1, mutex2);
+
+// Read-heavy data - use shared_mutex
+std::shared_lock readLock(sharedMutex);   // concurrent reads
+std::unique_lock writeLock(sharedMutex);  // exclusive write
+```
+
+**DON'T:**
+```cpp
+// NEVER nest lock_guard - causes deadlock
+std::lock_guard lock1(mutex1);
+std::lock_guard lock2(mutex2);  // DEADLOCK RISK
+```
+
+### ModuleLoader Usage
+- Each `ModuleLoader` instance manages ONE module lifecycle
+- Don't reuse loader for multiple independent modules (causes SEGFAULT)
+- `reload()` safely handles state extraction and library reload
+- `load(path, name, isReload=true)` for hot-reload with cache bypass
+
+## Known Issues
+- **TankModule.h linter bug**: A linter sometimes merges lines 35-36. If build fails with "logger not declared", check this file.
+
+## Test Categories
+| Test # | Name | Duration | Description |
+|--------|------|----------|-------------|
+| 1-10 | scenario_* | ~0.01s | Basic scenarios |
+| 11 | ProductionHotReload | ~12s | Full hot-reload cycle |
+| 12 | ChaosMonkey | ~41s | Stress testing |
+| 13 | StressTest | ~180s | Heavy load |
+| 15 | MemoryLeakHunter | ~135s | 200 reload cycles |
+| 19 | CrossSystemIntegration | ~4s | Multi-system test |
+
+## Debugging Tools
+```bash
+# ThreadSanitizer (detects data races, deadlocks)
+cmake -DGROVE_ENABLE_TSAN=ON -B build-tsan
+
+# Helgrind (alternative deadlock detector)
+cmake -DGROVE_ENABLE_HELGRIND=ON -B build
+make helgrind
+```