Revert the timeline optimistic and pagination rework (#2596)

* Add npm release track invariant and beta dist-tag procedure

* Revert "Keep older chat history and image previews stable (#2490)"

The timeline optimistic/pagination rework needs more work than main releases can wait for. Reverted together with #2484; both are reapplied on integration/timeline-optimistic-rework.

* Revert "Stop completed turns from appearing stuck (#2484)"

See the #2490 revert. #2490 built on this submission-authority change, so the two revert and reapply as a pair.

packages/app/src/assistant-image/file-acquisition.test.ts

@@ -1,53 +0,0 @@
-import { describe, expect, it } from "vitest";
-import type { AttachmentMetadata } from "@/attachments/types";
-import {
-  createAssistantImageFileAcquisition,
-  type AssistantImageFileAcquisitionPort,
-} from "./file-acquisition";
-
-class MemoryFileAcquisitionPort implements AssistantImageFileAcquisitionPort {
-  readonly reads: Array<{ cwd: string; path: string }> = [];
-
-  async readFile(cwd: string, path: string) {
-    this.reads.push({ cwd, path });
-    return {
-      kind: "image" as const,
-      path,
-      mime: "image/png",
-      size: 4,
-      modifiedAt: "1",
-      bytes: new Uint8Array([1, 2, 3, 4]),
-    };
-  }
-
-  async persist(input: { id: string; mimeType: string; fileName: string | null }) {
-    return {
-      id: input.id,
-      mimeType: input.mimeType,
-      storageType: "web-indexeddb" as const,
-      storageKey: input.id,
-      fileName: input.fileName,
-      byteSize: 4,
-      createdAt: 1,
-    } satisfies AttachmentMetadata;
-  }
-}
-
-describe("assistant image file acquisition", () => {
-  it("recreates the same acquisition with a live port after reconnect", async () => {
-    const common = {
-      resolution: { kind: "file_rpc" as const, cwd: "/workspace", path: "reconnect.png" },
-      serverId: "server",
-      occurrenceKey: "agent:message:reconnect-image",
-      unavailableMessage: "Image unavailable",
-    };
-    const disconnected = createAssistantImageFileAcquisition({ ...common, port: null });
-    const connectedPort = new MemoryFileAcquisitionPort();
-    const connected = createAssistantImageFileAcquisition({ ...common, port: connectedPort });
-
-    expect(disconnected?.key).toBe(connected?.key);
-    await expect(disconnected?.locate()).rejects.toThrow("Image unavailable");
-    await expect(connected?.locate()).resolves.toMatchObject({ mimeType: "image/png" });
-    expect(connectedPort.reads).toEqual([{ cwd: "/workspace", path: "reconnect.png" }]);
-  });
-});