Back up from a copy that decrypted even outside a run's albums; README wording

A file whose copy in an album in scope does not decrypt is now backed up
from a copy that decrypted in any album, not only one in scope; with no
such copy it is still recorded as failed. The README now says the exit
code stays at 1 until the server sends a copy that decrypts or deletes it,
and that only a run without --json prints the FAILED album line.
StoredMetadata.undecryptable is required, like the other fields.

Model: opus-5-5

src/backup.ts

@@ -609,9 +609,9 @@ const runLockedBackup = async (
 
     // What the library could not decrypt. An album is logged by its ID, as
     // its name is not known, so a run limited to some albums logs it too. A
-    // file in an album in scope is recorded as failed, with an empty title as
-    // its metadata is not known, unless a copy of it in another album
-    // decrypted.
+    // file in an album in scope is backed up from a copy of it in another
+    // album that decrypted, even an album out of scope. With no such copy it
+    // is recorded as failed, with an empty title as its metadata is not known.
     const scope = new Set(collections.map((c) => c.id));
     const undecryptableAlbums: number[] = [];
     for (const record of lib.undecryptable()) {
@@ -619,16 +619,18 @@ const runLockedBackup = async (
         if (record.fileID === undefined) {
             log(`FAILED album ${record.collectionID}: ${error}`);
             undecryptableAlbums.push(record.collectionID);
-        } else if (
-            scope.has(record.collectionID) &&
-            !memberships.has(record.fileID)
-        ) {
-            recordFailure(
-                record.fileID,
-                "",
-                collectionName.get(record.collectionID) ?? "",
-                new Error(error),
-            );
+        } else if (scope.has(record.collectionID)) {
+            const copies = memberships.get(record.fileID);
+            if (copies) {
+                distinct.set(record.fileID, representative(copies));
+            } else {
+                recordFailure(
+                    record.fileID,
+                    "",
+                    collectionName.get(record.collectionID) ?? "",
+                    new Error(error),
+                );
+            }
         }
     }
 

src/library/store.ts

@@ -49,7 +49,7 @@ interface StoredMetadata {
     collectionsSinceTime: Microseconds;
     collections: StoredCollection[];
     files: StoredFile[];
-    undecryptable?: Undecryptable[];
+    undecryptable: Undecryptable[];
 }
 
 const encodeKey = (key: Uint8Array): string =>