feat(app): store assistant image previews as assets

packages/app/src/attachments/web/indexeddb-attachment-store.ts

@@ -74,6 +74,15 @@ function runTx<T>(
   });
 }
 
+function base64ToBlob(input: { base64: string; mimeType: string }): Blob {
+  const binary = atob(input.base64);
+  const bytes = new Uint8Array(binary.length);
+  for (let index = 0; index < binary.length; index += 1) {
+    bytes[index] = binary.charCodeAt(index);
+  }
+  return new Blob([bytes], { type: input.mimeType });
+}
+
 async function sourceToBlob(input: SaveAttachmentInput): Promise<{ blob: Blob; mimeType: string }> {
   const source = input.source;
   if (source.kind === "blob") {
@@ -96,6 +105,14 @@ async function sourceToBlob(input: SaveAttachmentInput): Promise<{ blob: Blob; m
     };
   }
 
+  if (source.kind === "base64") {
+    const mimeType = normalizeMimeType(input.mimeType);
+    return {
+      blob: base64ToBlob({ base64: source.base64, mimeType }),
+      mimeType,
+    };
+  }
+
   const response = await fetch(source.uri);
   const blob = await response.blob();
   const mimeType = normalizeMimeType(input.mimeType ?? blob.type);