Implement reproducible S1 handoff contracts

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a02994-7685-7940-bf34-3555b8256018

schemas/s1-receipt.schema.json

@@ -0,0 +1,34 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://coulomb.social/schemas/railiance-infra/s1-receipt-v1.json",
+  "title": "Railiance S1 metadata-only receipt",
+  "type": "object",
+  "required": [
+    "schema_version",
+    "receipt_id",
+    "event_type",
+    "synthetic",
+    "created_at",
+    "source_revision",
+    "inventory_sha256",
+    "status"
+  ],
+  "properties": {
+    "schema_version": {"const": "1.0"},
+    "receipt_id": {"type": "string", "format": "uuid"},
+    "event_type": {
+      "enum": ["plan", "apply", "convergence", "verification", "rotation", "provisioning-chain"]
+    },
+    "synthetic": {"type": "boolean"},
+    "created_at": {"type": "string", "format": "date-time"},
+    "source_revision": {"type": "string", "pattern": "^[0-9a-f]{7,40}$"},
+    "inventory_sha256": {"type": "string", "pattern": "^[0-9a-f]{64}$"},
+    "status": {"enum": ["pass", "fail", "not-run"]},
+    "hosts": {"type": "array", "items": {"type": "string"}, "uniqueItems": true},
+    "profiles": {"type": "object", "additionalProperties": {"type": "string"}},
+    "evidence": {"type": "array"},
+    "links": {"type": "array"},
+    "phases": {"type": "array"}
+  },
+  "additionalProperties": true
+}