docs(code): document websocket flow

app/static/style.css

@@ -29,6 +29,7 @@ body {
   color: var(--text);
   background: var(--bg);
   direction: rtl;
+  /* The app shell owns scrolling so the page does not exceed the viewport. */
   overflow: hidden;
 }
 
@@ -98,6 +99,7 @@ h1 {
 }
 
 .layout {
+  /* Allows the chat and users panels to shrink and scroll inside the viewport. */
   min-height: 0;
   flex: 1;
   display: grid;
@@ -216,6 +218,7 @@ ul {
 
 #usersList {
   min-height: 0;
+  /* Long user lists scroll here instead of making the page taller. */
   overflow-y: auto;
 }
 
@@ -252,6 +255,7 @@ li {
   min-height: 0;
   flex: 1;
   padding: 18px;
+  /* Chat history scrolls inside the chat panel. */
   overflow-y: auto;
   display: flex;
   flex-direction: column;