docs: document package KV cache effects

packages/sdk/create-sdk/README.md

@@ -14,6 +14,8 @@ The provider choice is DeepSeek or a custom endpoint backed by `llm-pi-ai`. Deep
 
 Indirectly, through the generated project composition and its selected runtime plugins.
 
+**KV Cache effect**: No direct invalidation; the named consumer owns any request-prefix changes.
+
 ## Known Limitations and Deferred Work
 
 - **TTY-only creation** — flags prefill questions, but the wizard still requires an interactive terminal before it writes a project.