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

* fix(app): keep timeline history and previews stable

Treat persisted timeline replicas as display-only so authoritative pagination always comes from the daemon. Require renewed user intent between older-history pages unless the viewport genuinely remains at the history edge.

Model assistant image acquisition as loading, loaded, or failed so recreating a preview URL cannot be rendered as an error.

* fix(app): keep file image previews current

* fix(app): stabilize history pagination edges

* fix(app): recover transient timeline loads

* fix(app): retain assistant image previews

* Stabilize history pagination lifecycle

* Stabilize history settlement and image previews

* Retry file images after reconnect

* Keep active previews and pagination requests alive

* Replace image hook tests with typed ports

* Integrate timeline hydration with submission authority

* Harden pre-hydration timeline reconciliation

* Make rewind E2E use real scroll intent

* Preserve live timeline state through hydration

* Keep mounted image attachments retained

* Protect preview persistence and lifecycle hydration

* Preserve idless live assistant continuations

* Preserve timeline rows across delayed hydration

* test(app): cover real assistant image files

* Preserve assistant tool ordering during hydration

packages/app/src/utils/assistant-image-metadata.test.ts

@@ -3,7 +3,6 @@ import {
   clearAssistantImageMetadataCache,
   estimateAssistantMessageHeightFromCache,
   extractAssistantImageSources,
-  getAssistantImageLoadStateFromMetadata,
   getAssistantImageMetadata,
   setAssistantImageMetadata,
 } from "./assistant-image-metadata";
@@ -42,23 +41,6 @@ describe("assistant image metadata", () => {
     });
   });
 
-  it("maps missing metadata to the image loading state", () => {
-    expect(getAssistantImageLoadStateFromMetadata(null)).toEqual({ status: "loading" });
-  });
-
-  it("maps cached metadata to the image ready state", () => {
-    expect(
-      getAssistantImageLoadStateFromMetadata({
-        width: 900,
-        height: 1600,
-        aspectRatio: 9 / 16,
-      }),
-    ).toEqual({
-      status: "ready",
-      aspectRatio: 9 / 16,
-    });
-  });
-
   it("estimates assistant message height from cached image metadata", () => {
     setAssistantImageMetadata(
       {

packages/app/src/utils/assistant-image-metadata.ts

@@ -8,11 +8,6 @@ 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;
@@ -131,15 +126,6 @@ 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;