TEMPORARY: prove a failing test blocks the image

Will be reverted in the next commit. Verifying the gate rather than assuming it — the last
assumption of this kind was wrong for months.

src/test/java/com/itsthevine/web/GateProbeTest.java

@@ -0,0 +1,14 @@
+package com.itsthevine.web;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+/** TEMPORARY: proves a failing test actually stops the image being published. Removed immediately. */
+class GateProbeTest {
+
+    @Test
+    void deliberatelyFails() {
+        assertThat("the gate").isEqualTo("proved");
+    }
+}