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/load-dimensions.ts

@@ -1,45 +0,0 @@
-export interface AssistantImageDimensions {
-  width: number;
-  height: number;
-}
-
-interface AssistantImageDimensionCandidate {
-  width?: unknown;
-  height?: unknown;
-}
-
-export interface AssistantImageRenderedDimensionsReader {
-  read(renderedImage: unknown): AssistantImageDimensions | null;
-}
-
-function readPositiveDimensions(
-  candidate: AssistantImageDimensionCandidate | null | undefined,
-): AssistantImageDimensions | null {
-  if (
-    typeof candidate?.width !== "number" ||
-    typeof candidate.height !== "number" ||
-    candidate.width <= 0 ||
-    candidate.height <= 0
-  ) {
-    return null;
-  }
-  return { width: candidate.width, height: candidate.height };
-}
-
-export function resolveAssistantImageLoadDimensions(input: {
-  source?: AssistantImageDimensionCandidate | null;
-  target?: { naturalWidth?: unknown; naturalHeight?: unknown } | null;
-  renderedImage: unknown;
-  renderedDimensions: AssistantImageRenderedDimensionsReader;
-}): AssistantImageDimensions | null {
-  const source = readPositiveDimensions(input.source);
-  if (source) {
-    return source;
-  }
-
-  const target = readPositiveDimensions({
-    width: input.target?.naturalWidth,
-    height: input.target?.naturalHeight,
-  });
-  return target ?? input.renderedDimensions.read(input.renderedImage);
-}