fix: increase message list width (#3062)

### 🎯 Goal


https://linear.app/stream/issue/REACT-926/increase-message-list-max-width


https://www.notion.so/React-QA-New-Design-3206a5d7f9f680529d41c396be126d0b?d=3296a5d7f9f6806f8682001cc2c477e4&source=copy_link#3206a5d7f9f680348d74e2fd95d82cc9

### 🛠 Implementation details

_Provide a description of the implementation_

### 🎨 UI Changes

_Add relevant screenshots_

Author: szuperaz

src/components/MessageComposer/styling/MessageComposer.scss

@@ -34,7 +34,7 @@
   --str-chat__cooldown-border-inline-start: 0;
   --str-chat__cooldown-border-inline-end: 0;
   --str-chat__cooldown-box-shadow: none;
-  --str-chat__message-composer-max-width: 768px;
+  --str-chat__message-composer-max-width: 1120px;
   --str-chat__message-composer-padding: var(--spacing-md);
   --str-chat__message-composer-command-transition-duration: 280ms;
   --str-chat__message-composer-command-ease: cubic-bezier(0.22, 1, 0.32, 1);

src/components/MessageList/styling/MessageList.scss

@@ -13,7 +13,7 @@
 .str-chat__message-list-main-panel {
   --str-chat__message-list-scroll-max-width: calc(
     var(--str-chat__message-composer-max-width) +
-      var(--str-chat__message-composer-padding)
+      (2 * var(--str-chat__message-composer-padding))
   );
 }
 
@@ -30,7 +30,6 @@
 
   .str-chat__message-list-scroll {
     @include utils.message-list-spacing;
-    /* Max container 800px, 16px padding → 768px readable content; matches composer width + padding */
     max-width: var(--str-chat__message-list-scroll-max-width);
     .str-chat__ul {
       list-style: none;