README: state that development is primarily agent-driven

Surfaces the constraint that already shapes several kernel decisions
(GameObject/Component over ECS, explicit registration, the headless
introspection surface) instead of leaving it only in the internal spec.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N1qPfzq8TDCUMFMV3UwV5N

README.md

@@ -15,6 +15,16 @@ design decision:
 - **A small, frozen kernel.** Everything else — including the parts most
   engines treat as core — is a plugin, versioned and replaceable per project.
 
+## How this gets built
+
+Most of the code here — kernel and plugins alike — is written by an LLM
+coding agent rather than by hand. That's not incidental: it's a design
+input. It's why the object model is `GameObject`/`Component` instead of a
+hand-rolled ECS, why registration is verbose and explicit instead of
+convention-based, and why the engine has a headless, scriptable
+introspection surface no classic editor bothers with — see
+[`docs/kernel-contract.md`](docs/kernel-contract.md#7-written-by-an-agent-not-a-human).
+
 ## Status
 
 Pre-implementation. The current design is written up in