docs(readme): add development and cost guidance notice

Author: RandomOscillations

README.md

@@ -26,6 +26,12 @@ Extropy creates synthetic populations grounded in real-world distributions, conn
 
 **Simulate anything:** Policy changes. Pricing decisions. Product launches. Crisis response. Any scenario where humans form opinions, make decisions, and influence each other.
 
+## Development Notice
+
+- Extropy is still in active development and behavior may change between versions.
+- For reliable execution and triage, we strongly recommend running Extropy through an agentic harness (for example: Codex or Claude Code) rather than manual ad-hoc CLI usage.
+- Simulation can be expensive at scale (especially high-fidelity, multi-timestep runs). Start with small runs first; we recommend beginning at around `500` agents before scaling up.
+
 ## Install
 
 ```bash