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/go.mod

@@ -0,0 +1,13 @@
+module github.com/andydixon/vault
+
+// Go 1.26.6 or newer is a security requirement inherited from the crypto
+// library: the standard-library fixes it relies on exist only from that
+// release.
+go 1.26.6
+
+require (
+	github.com/cloudflare/circl v1.6.4
+	golang.org/x/crypto v0.53.0
+	golang.org/x/sys v0.46.0
+	golang.org/x/term v0.44.0
+)