fix(ui): stabilize task loading and live feeds (#13095)

Coordinate initial conversation reveal, preserve message identity and reading anchors during live updates, and bound transcript reads with recoverable retries. Cover desktop/mobile navigation and rich task loading with actual-route browser tests.

Verified all Linux CI gates, 5,575 local UI tests, eight layout browser scenarios, and recorded native Codex walkthroughs. Greptile: 5/5; all review findings resolved.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/components/task-chat/TaskChatThreadView.tsx

@@ -134,12 +134,10 @@ function renderItem(
       return (
         <TaskChatBubble
           item={item}
-          // Human messages are inserted optimistically and later replaced by
-          // their canonical server IDs. Animating either mount makes the same
-          // text visibly fade twice during that handoff; user sends should
-          // paint immediately and remain visually stable.
+          // Hydration and live-to-durable reconciliation may move a logical
+          // message between parents. Mounting must never replay a fade.
           animateEntry={
-            item.author !== "human" && !item.attachedTurn?.standaloneHeader
+            false
           }
           actions={
             item.attachedTurn?.standaloneHeader
@@ -372,7 +370,9 @@ export function TaskChatThreadView({
       {streamlined
         ? renderedItems.map(({ item, content }, index) => (
             <div
-              key={item.id}
+              key={item.kind === "message" ? item.renderKey ?? item.id : item.id}
+              data-thread-anchor={item.kind === "message" ? item.renderKey ?? item.id : item.id}
+              id={item.kind === "message" ? `comment-${item.id}` : undefined}
               className={taskChatItemSpacingClass(item, renderedItems[index - 1]?.item ?? null)}
               data-thread-item-kind={item.kind === "message" ? item.author : item.kind}
             >
@@ -381,7 +381,9 @@ export function TaskChatThreadView({
           ))
         : items.map((item, index) => (
             <div
-              key={item.id}
+              key={item.kind === "message" ? item.renderKey ?? item.id : item.id}
+              data-thread-anchor={item.kind === "message" ? item.renderKey ?? item.id : item.id}
+              id={item.kind === "message" ? `comment-${item.id}` : undefined}
               className={cn(
                 index > 0 &&
                   item.kind === "interaction" &&