feat: convert file manager into a plugin

plugins/file-manager/tests/frontend/optimistic-file-list.test.ts

@@ -0,0 +1,49 @@
+import { describe, expect, it } from "vitest";
+import type { FileItem } from "@/types/index";
+import {
+  addOptimisticItem,
+  childPath,
+  removePaths,
+  renameOptimisticItem,
+  restoreItems,
+} from "../../src/frontend/optimistic-file-list";
+
+const files: FileItem[] = [
+  { name: "alpha.txt", path: "/work/alpha.txt", type: "file", size: 10 },
+  { name: "docs", path: "/work/docs", type: "directory" },
+];
+
+describe("optimistic file list updates", () => {
+  it("builds child paths without duplicate separators", () => {
+    expect(childPath("/", "file.txt")).toBe("/file.txt");
+    expect(childPath("/work/", "file.txt")).toBe("/work/file.txt");
+  });
+
+  it("adds and rolls back a provisional item", () => {
+    const added = addOptimisticItem(files, "/work", "new.txt", "file", 0);
+    expect(added.at(-1)).toMatchObject({
+      name: "new.txt",
+      path: "/work/new.txt",
+      type: "file",
+      size: 0,
+    });
+    expect(removePaths(added, new Set(["/work/new.txt"]))).toEqual(files);
+  });
+
+  it("renames immediately and can reverse the same item", () => {
+    const renamed = renameOptimisticItem(files, "/work/alpha.txt", "beta.txt");
+    expect(renamed[0]).toMatchObject({
+      name: "beta.txt",
+      path: "/work/beta.txt",
+      size: 10,
+    });
+    expect(
+      renameOptimisticItem(renamed, "/work/beta.txt", "alpha.txt"),
+    ).toEqual(files);
+  });
+
+  it("restores only failed deletions without duplicating survivors", () => {
+    const remaining = removePaths(files, new Set(["/work/docs"]));
+    expect(restoreItems(remaining, [files[1], files[0]])).toEqual(files);
+  });
+});