docs(readme): add forge demo hero (gif + webp fallback)

Author: jddunn

README.md

@@ -39,6 +39,21 @@ On benchmarks: **85.6% on LongMemEval-S** at $0.0090 per correct answer (gpt-4o
 
 ---
 
+<div align="center">
+
+<picture>
+  <source srcset="https://raw.githubusercontent.com/framersai/agentos/master/assets/agentos-forge-demo.webp" type="image/webp" />
+  <img src="https://raw.githubusercontent.com/framersai/agentos/master/assets/agentos-forge-demo.gif"
+       alt="Three AgentOS agents with distinct HEXACO personalities collaborate on a code review, forge a new tool at runtime once they hit a gap their static toolkit can't cover, the LLM judge approves the spec, and all three invoke it on the next turn."
+       width="900" />
+</picture>
+
+<sub>Runtime tool forging + multi-agent collaboration. Reproduce with <code>node <a href="https://github.com/framersai/agentos/blob/master/examples/emergent-hierarchical-spawning.mjs">examples/emergent-hierarchical-spawning.mjs</a></code> — three commands, no API mocks.</sub>
+
+</div>
+
+---
+
 ## Install
 
 ```bash