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

src/main.cpp

@@ -0,0 +1,28 @@
+#include "kappa/package.hpp"
+
+#include <toml++/toml.hpp>
+#include <cstdlib>
+#include <exception>
+#include <filesystem>
+#include <iostream>
+
+int main(int argc, char* argv[]) {
+    std::filesystem::path toml_path = (argc > 1) ? argv[1] : "package.toml";
+
+    if (!std::filesystem::exists(toml_path)) {
+        std::cerr << "Error: '" << toml_path << "' not found\n";
+        return 1;
+    }
+
+    try {
+        auto pkg = kappa::parse_package(toml_path.native());
+        kappa::print_package(std::cout, pkg);
+        return 0;
+    } catch (const toml::parse_error& e) {
+        std::cerr << "Parse error:\n" << e << '\n';
+        return 1;
+    } catch (const std::exception& e) {
+        std::cerr << "Error: " << e.what() << '\n';
+        return 1;
+    }
+}