fix(hoverclient): send token: null (not empty string) on signin auth.json

pkg/hoverclient/client.go

@@ -102,7 +102,12 @@ func (c *Client) ensureLoginLocked(ctx context.Context) error {
 		"username": c.creds.Username,
 		"password": c.creds.Password,
 		"remember": false,
-		"token":    "",
+		// token MUST be JSON null, not "". Hover's signin branches on this
+		// field for its "magic token" sign-in: a non-null token (even "")
+		// routes to magic-token validation, which fails an empty token with
+		// a generic "Invalid username or password." The browser sends null
+		// for password sign-in; match it exactly (verified via DevTools).
+		"token": nil,
 	})
 	if err != nil {
 		return fmt.Errorf("hover signin step 1: %w", err)

pkg/hoverclient/client_test.go

@@ -143,8 +143,16 @@ func TestClient_Login_UsesBrowserSigninShape(t *testing.T) {
 		t.Fatalf("Login: %v", err)
 	}
 
-	if _, ok := authBody["token"]; !ok {
+	// Regression guard (do not weaken to a key-presence check): token MUST
+	// be JSON null, not "". A non-null token — including the empty string —
+	// routes Hover's auth.json to its "magic token" sign-in path, which
+	// fails an empty token with a generic "Invalid username or password"
+	// even when username + password are correct. Sending "" cost a
+	// multi-day live debugging session. See client.go ensureLoginLocked.
+	if v, ok := authBody["token"]; !ok {
 		t.Fatalf("auth body missing token field: %#v", authBody)
+	} else if v != nil {
+		t.Fatalf("token must be JSON null, got %#v — a non-null token (incl. \"\") triggers magic-token signin and 401s with valid creds", v)
 	}
 	if got := headers.Get("Origin"); got != hoverHost {
 		t.Errorf("Origin = %q, want %q", got, hoverHost)