feat: DSL parser, eval system, and project structure

- Hand-written lexer + recursive-descent parser for .kap package definitions
- Package constructs: const, license, provides, outputs, patches, depends
  (version-constrained, feature-gated, output-targeted), features (enabled/
  forced/flag), config files (default/replace/merge with cfg interpolation),
  env (?= soft-set), prepare/build/check/install phases
- Evaluator: recursive  resolver for prefix, jobopts, destdir, userargs,
  cfg.*, feature.*, package vars
- Comments: // single-line, /* */ multi-line
- /kappa/{bin,temp,db,system,system/builds} path layout
- Clang 22, C++23, CMake + vcpkg (tomlplusplus)
- .clangd + .clang-tidy configured

CMakeLists.txt

@@ -0,0 +1,33 @@
+cmake_minimum_required(VERSION 3.20)
+
+# Enforce Clang
+set(CMAKE_C_COMPILER clang)
+set(CMAKE_CXX_COMPILER clang++)
+
+project(kappa VERSION 0.1.0 LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 23)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+# Generate compile_commands.json for clangd
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+# --- vcpkg integration ---
+if(DEFINED ENV{VCPKG_ROOT})
+  set(CMAKE_TOOLCHAIN_FILE "$ENV{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake"
+      CACHE STRING "vcpkg toolchain")
+endif()
+
+find_package(tomlplusplus CONFIG REQUIRED)
+
+add_executable(kappa
+  src/main.cpp
+  src/package.cpp
+  src/paths.cpp
+  src/dsl/lexer.cpp
+  src/dsl/parser.cpp
+  src/eval/vars.cpp
+)
+target_include_directories(kappa PRIVATE include)
+target_link_libraries(kappa PRIVATE tomlplusplus::tomlplusplus)