Improve attachment memory safety, downloads, and high-memory alert UX.

Stream large receives to disk with chunk acks to cap renderer RAM, evict
off-screen display blobs, and route exports through a disk-aware download
service. Fix the high-memory dialog (backdrop dismiss, copy, log actions),
allow diagnostics paths in the path jail, and restore persisted image
hydration after reload.

Co-authored-by: Cursor <cursoragent@cursor.com>

toju-app/src/app/domains/direct-message/feature/dm-chat/dm-chat.component.ts

@@ -15,7 +15,6 @@ import { Store } from '@ngrx/store';
 import { toSignal } from '@angular/core/rxjs-interop';
 import { map } from 'rxjs';
 import { AppI18nService, APP_TRANSLATE_IMPORTS } from '../../../../core/i18n';
-import { ElectronBridgeService } from '../../../../core/platform/electron/electron-bridge.service';
 import { ViewportService } from '../../../../core/platform';
 import {
   BottomSheetComponent,
@@ -23,7 +22,11 @@ import {
   UserAvatarComponent
 } from '../../../../shared';
 import { DirectCallService } from '../../../direct-call';
-import { Attachment, AttachmentFacade } from '../../../attachment';
+import {
+  Attachment,
+  AttachmentDownloadService,
+  AttachmentFacade
+} from '../../../attachment';
 import { ThemeNodeDirective } from '../../../theme';
 import { DirectMessageService } from '../../application/services/direct-message.service';
 import { isConversationBound } from './dm-chat.rules';
@@ -88,7 +91,7 @@ export class DmChatComponent {
 
   private readonly route = inject(ActivatedRoute);
   private readonly store = inject(Store);
-  private readonly electronBridge = inject(ElectronBridgeService);
+  private readonly attachmentDownload = inject(AttachmentDownloadService);
   private readonly attachments = inject(AttachmentFacade);
   private readonly klipy = inject(KlipyService);
   private readonly linkMetadata = inject(LinkMetadataService);
@@ -485,49 +488,7 @@ export class DmChatComponent {
   }
 
   async downloadAttachment(attachment: Attachment): Promise<void> {
-    if (!attachment.available || !attachment.objectUrl) {
-      return;
-    }
-
-    const electronApi = this.electronBridge.getApi();
-
-    if (electronApi) {
-      const diskPath = this.getAttachmentDiskPath(attachment);
-
-      if (diskPath && electronApi.saveExistingFileAs) {
-        try {
-          const result = await electronApi.saveExistingFileAs(diskPath, attachment.filename);
-
-          if (result.saved || result.cancelled) {
-            return;
-          }
-        } catch {
-          /* fall back to blob/browser download */
-        }
-      }
-
-      const blob = await this.getAttachmentBlob(attachment);
-
-      if (blob) {
-        try {
-          const result = await electronApi.saveFileAs(attachment.filename, await this.blobToBase64(blob));
-
-          if (result.saved || result.cancelled) {
-            return;
-          }
-        } catch {
-          /* fall back to browser download */
-        }
-      }
-    }
-
-    const link = document.createElement('a');
-
-    link.href = attachment.objectUrl;
-    link.download = attachment.filename;
-    document.body.appendChild(link);
-    link.click();
-    document.body.removeChild(link);
+    await this.attachmentDownload.downloadToUserLocation(attachment);
   }
 
   async copyImageToClipboard(attachment: Attachment): Promise<void> {
@@ -599,48 +560,6 @@ export class DmChatComponent {
     return `${messageId}:${url}`;
   }
 
-  private async getAttachmentBlob(attachment: Attachment): Promise<Blob | null> {
-    if (!attachment.objectUrl) {
-      return null;
-    }
-
-    if (attachment.objectUrl.startsWith('file:')) {
-      return null;
-    }
-
-    try {
-      const response = await fetch(attachment.objectUrl);
-
-      return await response.blob();
-    } catch {
-      return null;
-    }
-  }
-
-  private getAttachmentDiskPath(attachment: Attachment): string | null {
-    return attachment.savedPath || attachment.filePath || null;
-  }
-
-  private blobToBase64(blob: Blob): Promise<string> {
-    return new Promise((resolve, reject) => {
-      const reader = new FileReader();
-
-      reader.onload = () => {
-        if (typeof reader.result !== 'string') {
-          reject(new Error('Failed to encode attachment'));
-          return;
-        }
-
-        const [, base64 = ''] = reader.result.split(',', 2);
-
-        resolve(base64);
-      };
-
-      reader.onerror = () => reject(reader.error ?? new Error('Failed to read attachment'));
-      reader.readAsDataURL(blob);
-    });
-  }
-
   private peerUserFor(conversation: NonNullable<ReturnType<typeof this.conversation>>): User | null {
     if (conversation.kind === 'group' || conversation.participants.length > 2) {
       return null;