playlists: make the writes actually leave the browser

Reported from a phone: signing in with the same account showed no
playlists. syncWith was called from exactly one place in the interface,
so creating a playlist, deleting one, removing a track and saving the
queue all wrote to IndexedDB and stopped there. The store pushes itself
now, coalesced, so a new mutation cannot forget to.

Silence was the real defect. The node audited only successes, so a
refusal left no trace and user_blob_list none at all; the background
push swallowed its reason; the interface said nothing. All three report
now, and "Sync now" says what happened either way.

An unreadable blob on a node was treated as a fetch failure and returned
before the push — permanent, once the node held anything. It is an
absence: the client is the authority, and it gets overwritten.

A sign-in reconciles whatever this browser already holds, a pending push
is flushed when the page goes away, and a push that did not land is
retried once.

no_key is spelled out: a client that signs in with its remembered device
key only ever has a bundle key persisted before the playlist subkey
existed, and an AES handle is non-extractable.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/playlist-menu.js b/packages/meshbay-hub/src/meshbay_hub/static/playlist-menu.js
index 8d85b68..e2fb3f9 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/playlist-menu.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/playlist-menu.js
@@ -183,7 +183,25 @@ function PlaylistMenuButton({ userId, lists, reload, onPlayQueue, onSync, cached
         onSelect: async () => {
           const r = await onSync();
           await reload();
-          say(r && r.ok ? t('playlists.synced') : t('playlists.sync_failed'));
+          // The reason, not just "it failed": a sync that quietly does nothing
+          // is the one failure mode nobody can act on, and the reason is what
+          // separates an offline node from a wedged one.
+          // On success, say how much moved; on failure, say why. Either way
+          // the reader learns something they can act on — the one thing this
+          // never did.
+          const last = P.lastSync();
+          const why = (r && r.reason) || last.reason || '?';
+          // `no_key` is not a fault the reader can do anything about unless it
+          // is spelled out. This browser signed in with its remembered device
+          // key, so the only bundle key it has is one persisted before the
+          // playlist subkey existed — and an AES handle is non-extractable, so
+          // there is nothing to derive it from. One sign-in with the passphrase
+          // fixes it for good; a code on screen does not say that.
+          say(r && r.ok
+            ? `${t('playlists.synced')} (${r.pushed || 0}↑ ${r.pulled || 0}↓)`
+            : (why === 'no_key'
+              ? t('playlists.err_no_key')
+              : `${t('playlists.sync_failed')}: ${why}`));
         },
       },
     ]);