test(08-03): add failing authorize RED test in wristband

- Server.Authorize stub returns 501
- TestPhase8RedAuthorize drives a full valid S256 request and asserts the
  exact 302 /connect success contract; fails with PHASE8_RED:authorize
  against the stub, verified fail-closed via check-phase8-red.sh

wristband/authorize_test.go

@@ -0,0 +1,119 @@
+package wristband
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+)
+
+// insertAuthorizeTestClient inserts an already-usable ClientRecord directly
+// into backend (bypassing CreateWithCap's cap/sweep policy, which this
+// plan's tests do not exercise) and returns it.
+func insertAuthorizeTestClient(backend *memoryBackend, clientID string, redirectURIs []string, ceiling []string) *ClientRecord {
+	backend.mu.Lock()
+	defer backend.mu.Unlock()
+	backend.nextID++
+	rec := &ClientRecord{
+		ID:                      backend.nextID,
+		ClientID:                clientID,
+		ClientName:              "Test Client",
+		RedirectURIs:            redirectURIs,
+		GrantTypes:              []string{"authorization_code", "refresh_token"},
+		TokenEndpointAuthMethod: "client_secret_post",
+		ScopeCeiling:            ceiling,
+		CreatedAt:               time.Now(),
+	}
+	backend.clients = append(backend.clients, rec)
+	return rec
+}
+
+// s256Pair returns a random PKCE verifier and its S256 challenge, matching
+// the byte transform every Phase 8 PHP/Go PKCE fixture shares.
+func s256Pair(t *testing.T) (verifier, challenge string) {
+	t.Helper()
+	v, err := randomBase64URL(32)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return v, s256Challenge(v)
+}
+
+// authorizeQuery builds a GET /oauth/mcp/authorize request from an ordered
+// param map (net/url.Values handles encoding fine for *requests*: only
+// response Location construction is bound by the RFC3986 ordered-pair
+// requirement).
+func authorizeRequest(params map[string]string) *http.Request {
+	q := url.Values{}
+	for k, v := range params {
+		q.Set(k, v)
+	}
+	return httptest.NewRequest(http.MethodGet, "/oauth/mcp/authorize?"+q.Encode(), nil)
+}
+
+// queryOf parses the query component of a redirect Location header into a
+// flat map (every Phase 8 authorize fixture uses at most one value per key).
+func queryOf(t *testing.T, location string) map[string]string {
+	t.Helper()
+	u, err := url.Parse(location)
+	if err != nil {
+		t.Fatalf("parse Location %q: %v", location, err)
+	}
+	out := map[string]string{}
+	for k, v := range u.Query() {
+		if len(v) > 0 {
+			out[k] = v[0]
+		}
+	}
+	return out
+}
+
+// TestPhase8RedAuthorize is the Phase 8 Wave 3 RED anchor (08-03-PLAN.md
+// Task 1, D-02/D-04/D-05). It drives one valid S256 authorize request
+// through the real (in-memory-backed) Server.Authorize and asserts the
+// exact success contract: 302 to <issuer>/connect?request=<opaque> with no
+// state/code leaked onto our own redirect and Cache-Control: no-store. It
+// fails with the PHASE8_RED:authorize sentinel while Authorize is the 501
+// stub; scripts/check-phase8-red.sh verifies this failure is fail-closed.
+func TestPhase8RedAuthorize(t *testing.T) {
+	backend := newMemoryBackend()
+	srv := newTestServer(backend)
+	insertAuthorizeTestClient(backend, "cli-red", []string{"https://chatgpt.com/connector/oauth/cb"}, nil)
+	_, challenge := s256Pair(t)
+
+	req := authorizeRequest(map[string]string{
+		"client_id":             "cli-red",
+		"redirect_uri":          "https://chatgpt.com/connector/oauth/cb",
+		"response_type":         "code",
+		"code_challenge":        challenge,
+		"code_challenge_method": "S256",
+		"scope":                 "read write",
+		"state":                 "must-not-appear-on-our-url",
+		"resource":              "https://mcp.plytarium.com/mcp",
+	})
+	rec := httptest.NewRecorder()
+	srv.Authorize(rec, req)
+
+	if rec.Code != http.StatusFound {
+		t.Fatalf("PHASE8_RED:authorize: status = %d, want %d (body=%s)", rec.Code, http.StatusFound, rec.Body.String())
+	}
+	loc := rec.Header().Get("Location")
+	if !strings.HasPrefix(loc, "https://plytarium.com/connect?") {
+		t.Fatalf("PHASE8_RED:authorize: Location = %q, want prefix \"https://plytarium.com/connect?\"", loc)
+	}
+	q := queryOf(t, loc)
+	if q["request"] == "" {
+		t.Fatalf("PHASE8_RED:authorize: Location %q missing non-empty request param", loc)
+	}
+	if _, has := q["state"]; has {
+		t.Fatalf("PHASE8_RED:authorize: Location %q leaks state onto our own redirect", loc)
+	}
+	if _, has := q["code"]; has {
+		t.Fatalf("PHASE8_RED:authorize: Location %q leaks a code onto our own redirect", loc)
+	}
+	if cc := rec.Header().Get("Cache-Control"); cc != "no-store" {
+		t.Fatalf("PHASE8_RED:authorize: Cache-Control = %q, want \"no-store\"", cc)
+	}
+}