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

.gitignore

@@ -32,3 +32,7 @@
 *.out
 *.app
 
+# Build
+build/
+compile_commands.json
+