Add Nix flake for mciasctl and mciasgrpcctl

Vendor dependencies and expose control program binaries via
nix build. Uses nixpkgs-unstable for Go 1.26 support.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/github.com/go-webauthn/webauthn/metadata/passkey_authenticator.go

@@ -0,0 +1,16 @@
+package metadata
+
+// PasskeyAuthenticator is a type that represents the schema from the Passkey Developer AAGUID listing.
+//
+// See: https://github.com/passkeydeveloper/passkey-authenticator-aaguids
+type PasskeyAuthenticator map[string]PassKeyAuthenticatorAAGUID
+
+// PassKeyAuthenticatorAAGUID is a type that represents the individual schema entry from the Passkey Developer AAGUID
+// listing. Used with [PasskeyAuthenticator].
+//
+// See: https://github.com/passkeydeveloper/passkey-authenticator-aaguids
+type PassKeyAuthenticatorAAGUID struct {
+	Name      string `json:"name"`
+	IconDark  string `json:"icon_dark,omitempty"`
+	IconLight string `json:"icon_light,omitempty"`
+}