M1: contracts and vectors (SPEC v0.1, schema 1)

contracts/openapi.yaml (OpenAPI 3.1, E-1..E-33, error shape and the
exhaustive error code enum, device bearer scheme), contracts/schema/
server-v1.sql (SPEC §14.1 verbatim), seven test-vector files per §14.5.5,
80 examples (every JSON body of §14.3.4, every error code, sync pull/push,
every FCM push type), and tools/contracts-check.py (stdlib-only reference
of §9.1, §9.3, §9.4 and §14.5.4 plus shape checks; the M1 gate).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

contracts/examples/E-12-create-invite/response.json

@@ -0,0 +1,9 @@
+{
+  "id": "0192a002-0000-7000-8000-000000000001",
+  "kind": "partner",
+  "target_user_id": null,
+  "code": "4N8RVT2KW6ZC",
+  "link": "https://icehack.asuscomm.com:8443/i/4N8RVT2KW6ZC",
+  "created_at": "2026-10-17T06:30:02.004Z",
+  "expires_at": "2026-10-20T06:30:02.004Z"
+}