Fix CI failures: Add conditional check for C++ source files

The C++ workflow was failing because no implementation files exist yet.
Added check-implementation job that verifies src/ directory exists before
running build/test jobs. All jobs now skip gracefully when C++ sources
are not yet implemented.

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>

dbal/cpp/IMPLEMENTATION_STATUS.md

@@ -0,0 +1,116 @@
+# C++ Implementation Status
+
+## Current State: Infrastructure Only
+
+The C++ DBAL implementation is currently in the **planning phase**. The following infrastructure has been set up:
+
+### ✅ Available
+- **Build System**: CMakeLists.txt with Conan + Ninja support
+- **Build Assistant**: `dbal/tools/cpp-build-assistant.js` for build automation
+- **CI/CD**: GitHub Actions workflow (`cpp-build.yml`) with conditional execution
+- **Project Structure**: Directory layout and header files
+- **Documentation**: Comprehensive README.md with architecture plans
+
+### ❌ Not Yet Implemented
+- **Source Files**: No `.cpp` implementation files exist yet
+- **Core Library**: Client, error handling, capabilities
+- **Query Engine**: AST, query builder, normalizer
+- **Database Adapters**: SQLite, MongoDB adapters
+- **Daemon**: Server, security implementation
+- **Tests**: Unit, integration, and conformance tests
+- **Utilities**: UUID generation, backoff strategies
+
+## Why CI is Skipped
+
+The GitHub Actions workflow includes a **check-implementation** job that:
+1. Checks if `dbal/cpp/src/` directory exists
+2. Verifies at least one `.cpp` file is present
+3. Sets `has_sources=false` if implementation is missing
+4. Skips all build/test jobs when sources don't exist
+
+This prevents CI failures while the C++ codebase is under development.
+
+## Implementation Roadmap
+
+### Phase 1: Core Types & Errors (Not Started)
+- [ ] `src/errors.cpp` - Error handling and Result type
+- [ ] `src/types.cpp` - Basic type system
+- [ ] `src/capabilities.cpp` - Capability detection
+
+### Phase 2: Query Builder (Not Started)
+- [ ] `src/query/ast.cpp` - Abstract syntax tree
+- [ ] `src/query/builder.cpp` - Query construction
+- [ ] `src/query/normalize.cpp` - Query normalization
+
+### Phase 3: Client (Not Started)
+- [ ] `src/client.cpp` - Main client interface
+- [ ] `src/util/uuid.cpp` - UUID generation
+- [ ] `src/util/backoff.cpp` - Retry logic
+
+### Phase 4: Adapters (Not Started)
+- [ ] `src/adapters/sqlite/sqlite_adapter.cpp`
+- [ ] `src/adapters/sqlite/sqlite_pool.cpp`
+
+### Phase 5: Daemon (Not Started)
+- [ ] `src/daemon/main.cpp` - Entry point
+- [ ] `src/daemon/server.cpp` - Server implementation
+- [ ] `src/daemon/security.cpp` - Security/ACL
+
+### Phase 6: Testing (Not Started)
+- [ ] `tests/unit/` - Unit tests
+- [ ] `tests/integration/` - Integration tests
+- [ ] `tests/conformance/` - Conformance tests
+
+## How to Start Implementation
+
+When you're ready to implement the C++ codebase:
+
+1. **Create the src directory**:
+   ```bash
+   mkdir -p dbal/cpp/src/{query,util,adapters/sqlite,daemon}
+   ```
+
+2. **Create a minimal main.cpp to test the build**:
+   ```bash
+   echo '#include <iostream>
+   int main() {
+       std::cout << "DBAL Daemon v0.1.0" << std::endl;
+       return 0;
+   }' > dbal/cpp/src/daemon/main.cpp
+   ```
+
+3. **Add stub implementations** for files referenced in CMakeLists.txt
+
+4. **Test the build locally**:
+   ```bash
+   npm run cpp:check
+   npm run cpp:full
+   ```
+
+5. **Commit and push** - CI will now detect sources and run builds
+
+## Why This Approach?
+
+**Benefits of conditional CI**:
+- ✅ No false-negative CI failures during development
+- ✅ Infrastructure is tested and ready when implementation begins
+- ✅ Clear signal when implementation starts (CI will activate)
+- ✅ Documentation and plans can be refined without CI noise
+
+**Alternative approaches considered**:
+- ❌ Disable workflow entirely - hides important infrastructure
+- ❌ Create stub implementations - creates technical debt
+- ❌ Mark as `continue-on-error` - hides real build failures
+
+## Questions?
+
+If you're working on the C++ implementation:
+- Check `dbal/cpp/README.md` for architecture details
+- Review `dbal/cpp/CMakeLists.txt` for build configuration
+- Use `dbal/tools/cpp-build-assistant.js` for build commands
+- See `.github/workflows/cpp-build.yml` for CI details
+
+---
+
+**Last Updated**: 2025-12-24  
+**Status**: Infrastructure Ready, Implementation Pending