feat(FN-4701): add no-changes-finalized reliability interaction test

Adds reliability interaction test coverage for the `no-changes-finalized` outcome (FN-4701), covering the benign case where verification-only done tasks complete with no owned commits or surviving branch.

Fusion-Task-Id: FN-4701

packages/engine/src/__tests__/reliability-interactions/no-changes-finalized.real-git.test.ts

@@ -0,0 +1,79 @@
+import { describe, it, expect, vi } from "vitest";
+import { classifyOwnedLandedEvidence } from "../../merger.js";
+import { makeReliabilityFixture, hasGit } from "./_helpers.js";
+
+describe("no-changes-finalized reliability interactions (real git)", () => {
+  it.skipIf(!hasGit)("reconciles verification-only done task without unproven warning", async () => {
+    const fixture = await makeReliabilityFixture({
+      taskId: "FN-4701-RI",
+      task: {
+        column: "done",
+        branch: undefined,
+        baseCommitSha: undefined,
+        mergeDetails: {},
+        modifiedFiles: ["docs/some-note.md"],
+      },
+    });
+
+    const { rootDir, task, store } = fixture;
+    await store.moveTask(task.id, "done");
+    await store.updateTask(task.id, {
+      branch: undefined,
+      baseCommitSha: undefined,
+      mergeDetails: {},
+      modifiedFiles: ["docs/some-note.md"],
+    });
+    const seededTask = (await store.getTask(task.id))!;
+
+    const logSpy = vi.spyOn(store, "logEntry");
+    const updateSpy = vi.spyOn(store, "updateTask");
+    const auditSpy = vi.spyOn(store, "recordRunAuditEvent");
+
+    try {
+      const classification = await classifyOwnedLandedEvidence(rootDir, seededTask, { mergeTargetBranch: "main" });
+      expect(classification.kind).toBe("no-changes-finalized");
+      expect(classification).toMatchObject({
+        baseRef: "main",
+        details: {
+          branchExists: false,
+          aheadCount: null,
+          baseReachableFromTarget: false,
+        },
+      });
+
+      const reconciled = await fixture.selfHeal.reconcileDoneTaskIntegrity();
+      expect(reconciled).toBeGreaterThanOrEqual(1);
+
+      const taskLogCalls = logSpy.mock.calls.filter((call) => call[0] === seededTask.id);
+      expect(taskLogCalls.some((call) => /done-task finalize evidence is unproven/.test(String(call[1] ?? "")))).toBe(false);
+
+      expect(updateSpy).toHaveBeenCalledWith(seededTask.id, expect.objectContaining({
+        modifiedFiles: [],
+        mergeDetails: expect.objectContaining({
+          mergeConfirmed: true,
+          noOpMerge: true,
+          noOpReason: "verification-only finalize: no branch and no owned commits",
+          landedFiles: [],
+        }),
+      }));
+
+      expect(
+        auditSpy.mock.calls.some(([event]) =>
+          (event as any)?.mutationType === "task:integrity-reconcile-modified-files" &&
+          (event as any)?.metadata?.reason === "verification-only-finalize"
+        ),
+      ).toBe(true);
+
+      const finalizeWarned = (fixture.manager as unknown as { finalizeUnprovenWarned: Set<string> }).finalizeUnprovenWarned;
+      expect(finalizeWarned.has(seededTask.id)).toBe(false);
+
+      await fixture.selfHeal.reconcileDoneTaskIntegrity();
+      const taskLogCallsAfterSecondRun = logSpy.mock.calls.filter((call) => call[0] === seededTask.id);
+      expect(
+        taskLogCallsAfterSecondRun.some((call) => /done-task finalize evidence is unproven/.test(String(call[1] ?? ""))),
+      ).toBe(false);
+    } finally {
+      await fixture.cleanup();
+    }
+  });
+});