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/output_writer.rs

@@ -0,0 +1,26 @@
+use std::cell::RefCell;
+
+use archlens_domain::{DomainError, RenderOutput, ports::OutputWriter};
+
+pub struct FakeOutputWriter {
+    written: RefCell<Vec<RenderOutput>>,
+}
+
+impl FakeOutputWriter {
+    pub fn new() -> Self {
+        Self {
+            written: RefCell::new(Vec::new()),
+        }
+    }
+
+    pub fn written_outputs(&self) -> Vec<RenderOutput> {
+        self.written.borrow().clone()
+    }
+}
+
+impl OutputWriter for FakeOutputWriter {
+    fn write(&self, output: &RenderOutput) -> Result<(), DomainError> {
+        self.written.borrow_mut().push(output.clone());
+        Ok(())
+    }
+}