Add relational world map and rename tech section

- Add EMERGENCE_WORLD_MAP.png to docs/, embedded in World Design
- Rename "Technical Architecture" -> "Stack at a Glance" (the table is a stack, not architecture; deeper doc still linked below)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -135,12 +135,19 @@ Key world features:
 - **🔧 120+ Interactive Tools** — Governance, research, social interaction, resource management, content creation, and more
 - **🌐 Real-World Capabilities** — Deep research, code execution, real-world news, shared world memory
 
+<p align="center">
+  <img src="docs/EMERGENCE_WORLD_MAP.png" alt="Emergence World — relational map of agents, tools, world, and subsystems" width="600"/>
+</p>
+<p align="center">
+  <em>How the pieces fit: agents act <strong>only</strong> through tools; tools are gated by location in the world.</em>
+</p>
+
 > Full landmark catalog → [`landmarks/`](landmarks/)  
 > Complete tool catalog → [`tools/`](tools/)
 
 ---
 
-## Technical Architecture
+## Stack at a Glance
 
 Emergence World is a full-stack system combining a 3D React frontend with a Python simulation backend: