Add hfviewer architecture card

Embed the hfviewer architecture visualization card in README.md.

README.md

@@ -26,3 +26,13 @@ Derived from stsb-bert-tiny-safetensors weights, unchanged.
 ## Evaluation
 
 Not evaluated - it is a plumbing test model.
+
+## Architecture graph
+
+<a href="https://hfviewer.com/HFVwr/bert-tiny-test?utm_source=huggingface&amp;utm_medium=embedded_model_card&amp;utm_campaign=HFVwr_bert-tiny-test_card" target="_blank" rel="noopener">
+  <img
+    src="https://hfviewer.com/api/card.svg?source=HFVwr%2Fbert-tiny-test&amp;granularity=0"
+    alt="Architecture graph for HFVwr/bert-tiny-test. Open in hfviewer"
+    width="100%"
+  />
+</a>