feat: add target repo examples and file layout guidance

examples/rust-project/ai/project-map.md

@@ -0,0 +1,10 @@
+# Project Map
+
+## Main structure
+- root crate or workspace declared in `Cargo.toml`
+- `src/main.rs` or `src/lib.rs` as primary entrypoints
+- `crates/` for workspace members where applicable
+
+## Notes
+- Distinguish unit tests from integration tests
+- Check whether feature flags alter build or test behavior