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

.clang-tidy

@@ -0,0 +1,15 @@
+Checks: >
+  -*,
+  bugprone-*,
+  modernize-*,
+  performance-*,
+  portability-*,
+  readability-*,
+  -modernize-use-trailing-return-type,
+  -readability-identifier-length,
+  -readability-magic-numbers,
+  -readability-identifier-naming
+
+CheckOptions:
+  - key: modernize-use-nullptr.NullptrMacros
+    value: 'NULL'