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/application/tests/fakes/file_discovery.rs

@@ -0,0 +1,27 @@
+use std::path::Path;
+
+use archlens_domain::{AnalysisConfig, DomainError, SourceFile, ports::FileDiscovery};
+
+pub struct FakeFileDiscovery {
+    files: Vec<SourceFile>,
+}
+
+impl FakeFileDiscovery {
+    pub fn new(files: Vec<SourceFile>) -> Self {
+        Self { files }
+    }
+
+    pub fn empty() -> Self {
+        Self { files: Vec::new() }
+    }
+}
+
+impl FileDiscovery for FakeFileDiscovery {
+    fn discover(
+        &self,
+        _root: &Path,
+        _config: &AnalysisConfig,
+    ) -> Result<Vec<SourceFile>, DomainError> {
+        Ok(self.files.clone())
+    }
+}