bootstrap: planned object-storage reef, no rail

Declare reef-storage as substrate_kind object-storage. Hold non-secret
attribute paths for Scaleway S3. Do not host a compute rail.

AGENTS.md

@@ -0,0 +1,17 @@
+# reef-storage — Agent Instructions
+
+## Repo Identity
+
+**Purpose:** Provider-delegated S3-compatible storage substrate. Owns
+non-secret operating attributes. Does not host a rail.
+
+**Domain:** financials  
+**Repo slug:** reef-storage  
+**Workplan prefix:** `REEF-STORAGE-WP-`
+
+## Standing rules
+
+- No rail. Scaleway (or a successor provider) operates S3.
+- No secrets in this repo. Cite `secret:railiance-platform/<id>`.
+- Attribute files are the source for `reef:storage/…#key` references.
+- Do not fold this substrate into `reef-railiance`.