fix: reject oversized checkout diffs (#2488)

* fix: reject oversized checkout diffs

* fix(diff): keep large previews from disconnecting clients

The physical socket limit is an OOM backstop, not a frame-size contract. Bound structured diff construction incrementally and report oversized previews without closing the client's socket.

* fix(app): preserve oversized diff state

* fix(diff): stay within relay frame limit

---------

Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>

packages/app/src/git/diff-pane.tsx

@@ -119,6 +119,7 @@ import {
   type InlineReviewActions,
 } from "@/review";
 import { usePublishWorkingDiffAttachment, useWorkingDiff } from "@/git/use-working-diff";
+import { DiffTooLargeState } from "@/git/diff-too-large-state";
 
 export type { GitActionId, GitAction, GitActions } from "@/git/policy";
 
@@ -1755,6 +1756,7 @@ interface DiffBodyContentProps {
   notGit: boolean;
   isDiffLoading: boolean;
   diffErrorMessage: string | null;
+  diffTooLarge: boolean;
   hasChanges: boolean;
   emptyMessage: string;
   children: ReactElement;
@@ -1768,6 +1770,7 @@ function DiffBodyContent({
   notGit,
   isDiffLoading,
   diffErrorMessage,
+  diffTooLarge,
   hasChanges,
   emptyMessage,
   children,
@@ -1803,6 +1806,9 @@ function DiffBodyContent({
       </View>
     );
   }
+  if (diffTooLarge) {
+    return <DiffTooLargeState />;
+  }
   if (diffErrorMessage) {
     return (
       <View style={styles.errorContainer}>
@@ -2693,6 +2699,7 @@ export function GitDiffPane({
     selectBase: handleSelectBase,
     files,
     diffPayloadError,
+    diffTooLarge,
     isDiffLoading,
     reviewActions,
     reviewAttachment,
@@ -2855,6 +2862,7 @@ export function GitDiffPane({
       notGit={notGit}
       isDiffLoading={isDiffLoading}
       diffErrorMessage={diffErrorMessage}
+      diffTooLarge={diffTooLarge}
       hasChanges={hasChanges}
       emptyMessage={emptyMessage}
       checkingRepositoryLabel={t("workspace.git.diff.checkingRepository")}