feat: add last-turn diff view

Adds a Last turn scope to DiffView that renders OpenCode snapshot diffs from the latest user message summary without re-fetching git contents. The view hides Review in that mode and carries the selected diff scope through main and context-panel navigation.

Connects latest-turn changed-file chips in chat to the snapshot diff view on desktop and mobile, while keeping older turn chips static/read-only to avoid misleading affordances and extra subscriptions. Updates localized labels and empty states plus changelog.

Validation: bun run type-check (packages/ui); bun run lint (packages/ui).

packages/ui/src/components/chat/message/MessageBody.tsx

@@ -65,37 +65,88 @@ const getDisplayFileName = (file: string): string => {
     return segments.at(-1) ?? file;
 };
 
-const TurnChangedFilePills = React.memo(({ files }: { files?: TurnChangedFile[] }) => {
-    if (!files || files.length === 0) {
-        return null;
-    }
+const TurnChangedFileChipContent = React.memo(({ file, interactive = false }: { file: TurnChangedFile; interactive?: boolean }) => (
+    <span
+        className={cn(
+            'inline-flex max-w-full items-center gap-1.5 rounded-lg border border-border/30 bg-muted/30 px-2 py-1 text-xs leading-[1.35] text-muted-foreground',
+            interactive && 'transition-colors hover:border-border/60 hover:bg-interactive-hover'
+        )}
+    >
+        <FileTypeIcon filePath={file.file} className="h-3.5 w-3.5 flex-shrink-0" />
+        <span className="max-w-52 truncate text-foreground/80" title={file.file}>{getDisplayFileName(file.file)}</span>
+        <span className="flex-shrink-0 inline-flex items-center gap-0 typography-meta" style={{ fontSize: '0.8rem', lineHeight: '1' }}>
+            <span style={{ color: 'var(--status-success)' }}>+{file.additions}</span>
+            <span className="text-muted-foreground/70">/</span>
+            <span style={{ color: 'var(--status-error)' }}>-{file.deletions}</span>
+        </span>
+    </span>
+));
+
+const TurnChangedFilePillButton = React.memo(({
+    file,
+    onOpen,
+}: {
+    file: TurnChangedFile;
+    onOpen: (file: string) => void;
+}) => {
+    const { t } = useI18n();
+    return (
+        <button
+            type="button"
+            className="inline-flex h-8 max-w-full cursor-pointer items-center rounded-lg outline-none focus-visible:ring-2 focus-visible:ring-[var(--interactive-focus-ring)]"
+            aria-label={t('chat.changedFiles.actions.openFileTitle', { path: file.file })}
+            title={file.file}
+            onClick={(event) => {
+                event.preventDefault();
+                event.stopPropagation();
+                onOpen(file.file);
+            }}
+        >
+            <TurnChangedFileChipContent file={file} interactive />
+        </button>
+    );
+});
+
+const StaticTurnChangedFilePills = React.memo(({ files }: { files: TurnChangedFile[] }) => (
+    <>
+        {files.map((file) => (
+            <span key={file.file} className="inline-flex h-8 max-w-full items-center" title={file.file}>
+                <TurnChangedFileChipContent file={file} />
+            </span>
+        ))}
+    </>
+));
+
+const InteractiveTurnChangedFilePills = React.memo(({ files }: { files: TurnChangedFile[] }) => {
+    const effectiveDirectory = useEffectiveDirectory();
+    const isMobile = useUIStore((state) => state.isMobile);
+    const navigateToDiff = useUIStore((state) => state.navigateToDiff);
+    const openContextDiff = useUIStore((state) => state.openContextDiff);
+
+    const openLastTurnDiff = React.useCallback((file: string) => {
+        if (!isMobile && effectiveDirectory) {
+            openContextDiff(effectiveDirectory, file, false, 'turn');
+            return;
+        }
+
+        navigateToDiff(file, false, 'turn');
+    }, [effectiveDirectory, isMobile, navigateToDiff, openContextDiff]);
 
     return (
         <>
-            {files.map((file) => {
-                return (
-                    <Tooltip key={file.file}>
-                        <TooltipTrigger asChild>
-                            <span className="inline-flex h-8 max-w-full items-center">
-                                <span className="inline-flex max-w-full items-center gap-1.5 rounded-lg border border-border/30 bg-muted/30 px-2 py-1 text-xs leading-[1.35] text-muted-foreground">
-                                    <FileTypeIcon filePath={file.file} className="h-3.5 w-3.5 flex-shrink-0" />
-                                    <span className="max-w-52 truncate text-foreground/80" title={file.file}>{getDisplayFileName(file.file)}</span>
-                                    <span className="flex-shrink-0 inline-flex items-center gap-0 typography-meta" style={{ fontSize: '0.8rem', lineHeight: '1' }}>
-                                        <span style={{ color: 'var(--status-success)' }}>+{file.additions}</span>
-                                        <span className="text-muted-foreground/70">/</span>
-                                        <span style={{ color: 'var(--status-error)' }}>-{file.deletions}</span>
-                                    </span>
-                                </span>
-                            </span>
-                        </TooltipTrigger>
-                        <TooltipContent>{file.file}</TooltipContent>
-                    </Tooltip>
-                );
-            })}
+            {files.map((file) => (
+                <TurnChangedFilePillButton key={file.file} file={file} onOpen={openLastTurnDiff} />
+            ))}
         </>
     );
 });
 
+const TurnChangedFilePills = React.memo(({ files, isInteractive }: { files?: TurnChangedFile[]; isInteractive: boolean }) => {
+    if (!files || files.length === 0) return null;
+
+    return isInteractive ? <InteractiveTurnChangedFilePills files={files} /> : <StaticTurnChangedFilePills files={files} />;
+});
+
 type SubtaskPartLike = Part & {
     type: 'subtask';
     description?: unknown;
@@ -2079,7 +2130,10 @@ const AssistantMessageBody = React.memo(({
                             <TurnChangedFilesDropdown activityParts={turnGroupingContext?.activityParts} />
                         ) : null}
                         {!isMiniChatSurface && isLastAssistantInTurn && hasStopFinish ? (
-                            <TurnChangedFilePills files={turnGroupingContext?.changedFiles} />
+                            <TurnChangedFilePills
+                                files={turnGroupingContext?.changedFiles}
+                                isInteractive={turnGroupingContext?.isLatestTurn === true}
+                            />
                         ) : null}
                     </div>
                 )}

packages/ui/src/components/chat/message/renderCompare.ts

@@ -280,6 +280,7 @@ export const areRelevantTurnGroupingContextsEqual = (
   if (left.turnId !== right.turnId) return false;
   if (left.isFirstAssistantInTurn !== right.isFirstAssistantInTurn) return false;
   if (left.isLastAssistantInTurn !== right.isLastAssistantInTurn) return false;
+  if (left.isLatestTurn !== right.isLatestTurn) return false;
   if (left.isWorking !== right.isWorking) return false;
   if (left.hasTools !== right.hasTools) return false;
   if (left.hasReasoning !== right.hasReasoning) return false;