test(08-01): add failing RFC 8414 metadata RED test and fail-closed verifier

- wristband.Server.Metadata is a compiling 501 stub; TestPhase8RedMetadata
  asserts the exact unwrapped PHP metadata document, headers and status and
  fails with the PHASE8_RED:metadata sentinel (D-06)
- scripts/check-phase8-red.sh implements the shared go/shell RED contract
  for the rest of Phase 8: exact selected test/package failure plus sentinel,
  rejecting unrelated fail actions, compile/setup failures, panics,
  malformed JSON, missing/duplicate sentinels and zero selection (D-04/D-18)

wristband/server.go

@@ -0,0 +1,72 @@
+// Package wristband implements the app-agnostic RFC 8414 / OAuth
+// authorization-server surface ported from Płytarium's hand-rolled PHP OAuth
+// server (08-CONTEXT.md D-05). It never imports an application package, a
+// GORM type, or any fonoteka model: every deployment-specific value (issuer,
+// scopes, endpoint paths, TTLs) arrives through Options, and every app-owned
+// concern (users, collections, persistence) stays out of this package.
+//
+// D-06: PHP's RFC-minimal response shapes are wristband's defaults. There
+// are no response hooks; callers cannot alter the wire bytes beyond the
+// values exposed on Options.
+package wristband
+
+import "net/http"
+
+// Options configures a Server's advertised endpoints and metadata values.
+// Every field has a PHP-parity default via DefaultOptions except Issuer,
+// which the caller must set from app.url with its trailing slash trimmed
+// exactly once (D-03). wristband never hardcodes an app's issuer.
+type Options struct {
+	// Issuer is app.url with exactly one trailing slash trimmed by the
+	// caller. Every metadata endpoint URL is built by appending a fixed
+	// RFC path suffix to Issuer.
+	Issuer string
+
+	// ServiceDocumentationPath is appended to Issuer for the metadata
+	// service_documentation field. PHP default: "/help".
+	ServiceDocumentationPath string
+
+	// ScopesSupported is the RFC 8414 scopes_supported list. PHP default:
+	// ["read","write","ai","offline_access"].
+	ScopesSupported []string
+
+	// TokenEndpointAuthMethodsSupported is the RFC 8414
+	// token_endpoint_auth_methods_supported list. PHP default:
+	// ["none","client_secret_post","client_secret_basic"].
+	TokenEndpointAuthMethodsSupported []string
+
+	// AuthorizationResponseIssParameterSupported is the RFC 9207 metadata
+	// capability flag. PHP default: true.
+	AuthorizationResponseIssParameterSupported bool
+}
+
+// DefaultOptions returns PHP-parity defaults for every metadata option
+// other than Issuer, which the caller must set from app.url.
+func DefaultOptions() Options {
+	return Options{
+		ServiceDocumentationPath:                   "/help",
+		ScopesSupported:                            []string{"read", "write", "ai", "offline_access"},
+		TokenEndpointAuthMethodsSupported:          []string{"none", "client_secret_post", "client_secret_basic"},
+		AuthorizationResponseIssParameterSupported: true,
+	}
+}
+
+// Server is the app-agnostic wristband authorization-server surface. It is
+// constructed with Options and never imports an application package.
+type Server struct {
+	opts Options
+}
+
+// NewServer constructs a Server from Options.
+func NewServer(opts Options) *Server {
+	return &Server{opts: opts}
+}
+
+// Metadata handles GET /.well-known/oauth-authorization-server, writing the
+// exact unwrapped RFC 8414 document (D-06).
+//
+// TODO(08-01 Task 2): wire the exact writer and PHP-parity document; this
+// stub intentionally does not yet satisfy TestPhase8RedMetadata.
+func (s *Server) Metadata(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusNotImplemented)
+}