FIX: minor chat styleguide fixes (#23849)

- makes message take full width
- allows to remove the thread state
- removes non-existing component (mention warning)

plugins/chat/assets/javascripts/discourse/components/styleguide/organisms/chat.hbs

@@ -3,7 +3,6 @@
 <Styleguide::ChatThreadListItem />
 <Styleguide::ChatComposerMessageDetails />
 <Styleguide::ChatHeaderIcon />
-<Styleguide::ChatMessageMentionWarning />
 
 <h2>Modals</h2>
 

plugins/chat/assets/javascripts/discourse/models/chat-message.js

@@ -115,6 +115,11 @@ export default class ChatMessage {
   }
 
   set thread(thread) {
+    if (!thread) {
+      this._thread = null;
+      return;
+    }
+
     this._thread = this.channel.threadsManager.add(this.channel, thread, {
       replace: true,
     });

plugins/chat/assets/stylesheets/common/chat-message.scss

@@ -177,6 +177,7 @@
 
 .chat-message-container {
   background-color: var(--d-content-background, var(--secondary));
+  width: 100%;
 
   &.-errored {
     color: var(--primary-medium);