readme: place SDK diagram below the intro (slightly smaller)

Author: blackwell-systems

README.md

@@ -13,6 +13,10 @@
 
 Python implementation of [GCF](https://gcformat.com/) — the most token-efficient wire format for LLMs. A drop-in alternative to JSON and TOON for any structured data.
 
+<p align="center">
+  <img src="assets/gcf-python-diagram.png" alt="gcf-python" width="80%">
+</p>
+
 **Built for the agentic loop, where the same structured context crosses the model boundary turn after turn.** A single payload is 50-92% smaller than JSON, but GCF also deduplicates repeated structure across turns and sends only deltas when context changes, so by the 5th overlapping call each response costs 99% fewer tokens than JSON, and a 10-call session runs 94.4% cheaper than re-sending JSON every turn. Session dedup and delta both need local IDs and a multi-turn design that neither JSON nor TOON has.
 
 - **100% comprehension on every frontier model**, zero training. 29% fewer tokens than TOON and 56% fewer than JSON across 16 datasets; 91.2% on structurally complex code graphs (vs TOON 68.8%, JSON 54.1%).