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/library/store.ts

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