Add design references, editor settings and todo

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.vscode/settings.json

@@ -0,0 +1,10 @@
+{
+  "files.associations": {
+    "*.tcc": "cpp",
+    "deque": "cpp",
+    "string": "cpp",
+    "unordered_map": "cpp",
+    "vector": "cpp",
+    "system_error": "cpp"
+  }
+}