Add Codex repo-specific tracking structure

Codex/API/README.md

@@ -0,0 +1,19 @@
+# API Codex
+
+Repo: `jester/zpack-api`
+
+Use this folder to track API-only work.
+
+Read in this order:
+1. `CURRENT_STATE.md`
+2. `OPEN_ITEMS.md`
+3. `DECISIONS.md`
+
+Scope:
+- agent transport and contract handling
+- API readiness semantics
+- backup forwarding and response contracts
+- billing/auth/API-side lifecycle flows
+- hosted IDE/API-side proxy and token flow
+
+Do not put Portal-only or Agent-only implementation details here unless they directly affect API behavior or integration.