feat(lifecycle): define durable deletion state vocabulary

src/main/java/com/clearfolio/viewer/lifecycle/ArtifactDeletionState.java

@@ -0,0 +1,33 @@
+package com.clearfolio.viewer.lifecycle;
+
+/**
+ * Durable states in the artifact-deletion receipt lifecycle.
+ */
+public enum ArtifactDeletionState {
+    /**
+     * An authorized deletion request has been durably accepted. The receipt may
+     * still carry the controlled pre-snapshot marker until an exact artifact
+     * checksum is captured; metadata cannot be tombstoned before that binding.
+     */
+    DELETION_REQUESTED,
+
+    /**
+     * Tenant-owned job metadata has been tombstoned.
+     */
+    METADATA_TOMBSTONED,
+
+    /**
+     * Exact-generation artifact cleanup is ready for a worker attempt.
+     */
+    ARTIFACT_CLEANUP_PENDING,
+
+    /**
+     * Artifact cleanup completed and the receipt is terminal.
+     */
+    ARTIFACT_CLEANUP_COMPLETED,
+
+    /**
+     * Artifact cleanup failed and remains eligible for a controlled retry.
+     */
+    ARTIFACT_CLEANUP_FAILED
+}

src/test/java/com/clearfolio/viewer/lifecycle/ArtifactDeletionStateTest.java

@@ -0,0 +1,28 @@
+package com.clearfolio.viewer.lifecycle;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Verifies the durable deletion state vocabulary used by lifecycle receipts.
+ */
+class ArtifactDeletionStateTest {
+
+    @Test
+    void exposesOnlyTheMonotonicDeletionLifecycleStates() {
+        ArtifactDeletionState[] expected = {
+            ArtifactDeletionState.DELETION_REQUESTED,
+            ArtifactDeletionState.METADATA_TOMBSTONED,
+            ArtifactDeletionState.ARTIFACT_CLEANUP_PENDING,
+            ArtifactDeletionState.ARTIFACT_CLEANUP_COMPLETED,
+            ArtifactDeletionState.ARTIFACT_CLEANUP_FAILED
+        };
+
+        assertArrayEquals(expected, ArtifactDeletionState.values());
+        for (ArtifactDeletionState state : expected) {
+            assertSame(state, ArtifactDeletionState.valueOf(state.name()));
+        }
+    }
+}