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/src/ports/diagram_renderer.rs

@@ -0,0 +1,5 @@
+use crate::{CodeGraph, DomainError, RenderOutput};
+
+pub trait DiagramRenderer {
+    fn render(&self, graph: &CodeGraph) -> Result<RenderOutput, DomainError>;
+}