Follow a conversation being read somewhere else

Opening a conversation now tells the service as well as the local
notifier, and a read announced from another device clears the count here.
Both go through one call the daemon quietly ignores on protocols with no
read state, so the renderer does not need to know which is which.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/renderer/src/state/store.ts

@@ -705,6 +705,17 @@ export class ChatStore {
         this.handleBufferListChange(data)
         break
 
+      // Read on another device. Discord echoes an ack to every session an
+      // account has, including the one that sent it, so this settles our own
+      // count as well as following somebody's phone.
+      case 'bufferRead':
+        this.set({
+          buffers: this.state.buffers.map((b) =>
+            b.id === data.bufferId ? { ...b, unread: 0, highlight: false } : b
+          )
+        })
+        break
+
       case 'bufferGroupChange':
         // A leave arrives as a removal rather than a new shape. Passing that
         // to the upsert would add a rail entry with no name and no service.
@@ -1045,6 +1056,10 @@ export class ChatStore {
     }
     void window.moho.markBufferRead(bufferId)
     bestEffort(this.markRead(bufferId), 'mark read')
+    // And tell the service, where the service has anywhere to put it, so a
+    // conversation read here stops being unread on somebody's phone. A no-op
+    // on protocols with no read state, so it needs no test of which this is.
+    bestEffort(window.moho.rpc('markBufferRead', { bufferId }), 'ack read')
     bestEffort(window.moho.rpc('subscribe', { bufferId }), `subscribe ${bufferId}`)
 
     // Discord only sends a member list for the channel being looked at, and