Freeze the Go implementation as a test-only oracle, with vectors

oracle/go is the Go code at 4c1507c, moved unchanged, plus test-only
generators that record what it computes. tests/vectors holds the
deterministic crypto/store vectors and synthetic fixtures they produce.

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

oracle/go/agent_other.go

@@ -0,0 +1,13 @@
+// Copyright 2026 The vault Authors.
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+//go:build !unix
+
+package main
+
+// ponytail: no memory locking off unix; VirtualLock on Windows if wanted.
+func protectMemory([]byte) {}
+
+// privateDir trusts the per-user temporary directory; Windows keeps it
+// private with its ACL.
+func privateDir(string) error { return nil }