init: archlens — architecture diagram generator

Hex arch + DDD, tree-sitter parsing, Mermaid/ASCII output.
Supports Rust + Python. 92 tests. CI, diff, --check for staleness detection.

crates/domain/tests/source_file_tests.rs

@@ -0,0 +1,10 @@
+use archlens_domain::{FilePath, Language, SourceFile};
+
+#[test]
+fn source_file_carries_path_and_language() {
+    let path = FilePath::new("src/main.rs").unwrap();
+    let file = SourceFile::new(path.clone(), Language::Rust);
+
+    assert_eq!(file.path(), &path);
+    assert_eq!(file.language(), Language::Rust);
+}