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/utils/assistant-image-metadata.ts

@@ -8,6 +8,11 @@ export interface AssistantImageMetadata {
   aspectRatio: number;
 }
 
+export type AssistantImageLoadState =
+  | { status: "loading" }
+  | { status: "ready"; aspectRatio: number }
+  | { status: "error" };
+
 const assistantImageMetadataCache = new Map<string, AssistantImageMetadata>();
 const assistantImageParseCache = new Map<string, { sources: string[]; hasNonImageText: boolean }>();
 const ASSISTANT_IMAGE_METADATA_CACHE_LIMIT = 500;
@@ -126,6 +131,15 @@ export function getAssistantImageMetadata(input: {
   return null;
 }
 
+export function getAssistantImageLoadStateFromMetadata(
+  metadata: AssistantImageMetadata | null,
+): AssistantImageLoadState {
+  if (!metadata) {
+    return { status: "loading" };
+  }
+  return { status: "ready", aspectRatio: metadata.aspectRatio };
+}
+
 export function setAssistantImageMetadata(
   input: {
     source: string;