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/attachment/domain/logic/attachment-image.rules.spec.ts

@@ -7,6 +7,7 @@ import {
 import {
   dedupeImageAttachmentsForDisplay,
   hasImageFilename,
+  isAttachmentPendingInlineHydration,
   isImageAttachment,
   isInlineDisplayableImage,
   resolvePublishAttachmentIsImage
@@ -38,6 +39,27 @@ describe('attachment-image rules', () => {
     })).toBe(true);
   });
 
+  it('detects images waiting for on-demand blob hydration', () => {
+    expect(isAttachmentPendingInlineHydration({
+      id: '1',
+      filename: 'photo.png',
+      mime: 'image/png',
+      isImage: true,
+      available: false,
+      savedPath: '/appdata/photo.png'
+    })).toBe(true);
+
+    expect(isAttachmentPendingInlineHydration({
+      id: '2',
+      filename: 'photo.png',
+      mime: 'image/png',
+      isImage: true,
+      available: true,
+      objectUrl: 'blob:http://localhost/photo',
+      savedPath: '/appdata/photo.png'
+    })).toBe(false);
+  });
+
   it('dedupes image attachments by filename and prefers displayable copies', () => {
     const deduped = dedupeImageAttachmentsForDisplay([
       {