feat: add BuildCodeGraph use case, sink orchestration out of presentation

crates/application/tests/fakes/project_analyzer.rs

@@ -0,0 +1,23 @@
+use std::path::Path;
+
+use archlens_domain::{CodeGraph, DomainError, ports::ProjectAnalyzer};
+
+pub struct FakeProjectAnalyzer {
+    graph: CodeGraph,
+}
+
+impl FakeProjectAnalyzer {
+    pub fn new(graph: CodeGraph) -> Self {
+        Self { graph }
+    }
+
+    pub fn empty() -> Self {
+        Self { graph: CodeGraph::new() }
+    }
+}
+
+impl ProjectAnalyzer for FakeProjectAnalyzer {
+    fn analyze(&self, _root: &Path) -> Result<CodeGraph, DomainError> {
+        Ok(self.graph.clone())
+    }
+}