Fix up spots where we still tried to treat `remote.channels.all` as a map.

In ae93188f0f4f36086622636ba9ae4810cbd1f8c9, `remote.channels.all` became a flat array of channels, instead of a map, in order to simplify some of the reasoning around how state changes propagate. However, I neglected to remove all Map-shaped calls referring to it.

This lead to some pretty interesting behaviour:

* The client could not track unread state, because reconciling local state against the remote state would find no remote state, then throw away local state entirely as a result.
* The client would not actually update when a new channel appeared.
* The client would not actually update when a channel disappeared.

1 files changed, 2 insertions, 1 deletions

diff --git a/ui/lib/state/local/channels.svelte.js b/ui/lib/state/local/channels.svelte.js
index d86d028..e3ee8df 100644
--- a/ui/lib/state/local/channels.svelte.js
+++ b/ui/lib/state/local/channels.svelte.js
@@ -82,7 +82,8 @@ export class Channels {
     }
   }
 
-  retainChannels(channelIds) {
+  retainChannels(channels) {
+    const channelIds = channels.map((channel) => channel.id);
     const retain = new Set(channelIds);
     for (const channelId of Array.from(this.all.keys())) {
       if (!retain.has(channelId)) {