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/diagram_renderer.rs

@@ -0,0 +1,17 @@
+use archlens_domain::{CodeGraph, DomainError, RenderOutput, RenderedFile, ports::DiagramRenderer};
+
+pub struct FakeDiagramRenderer;
+
+impl FakeDiagramRenderer {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl DiagramRenderer for FakeDiagramRenderer {
+    fn render(&self, graph: &CodeGraph) -> Result<RenderOutput, DomainError> {
+        let content = format!("graph with {} elements", graph.elements().len());
+        let file = RenderedFile::new("output.mmd", &content)?;
+        Ok(RenderOutput::single(file))
+    }
+}