floating action pill + auto-scroll on send + channel ordering

- Actions: floating pill top-right with ↩ and × (slides in on hover)
- No more ugly REPLY DEL text — minimal symbols, backdrop shadow
- Delete button only shows for own messages
- Auto-scroll to bottom after sending a message
- Channels sorted by last opened in sidebar

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/colony/src/components/MessageItem.tsx

@@ -149,26 +149,31 @@ export function MessageItem({ message, replyTarget, onReply, onDelete, currentUs
             </Tooltip>
           </TooltipProvider>
 
-          {/* Actions */}
-          <div className="ml-auto flex items-center gap-1 md:opacity-0 md:group-hover:opacity-100 transition-opacity">
+        </div>
+
+        {/* Floating action pill — top-right, appears on hover */}
+        {!isDeleted && (
+          <div className="absolute -top-3 right-3 md:opacity-0 md:translate-y-1 md:group-hover:opacity-100 md:group-hover:translate-y-0 transition-all duration-150 flex border-2 border-border bg-card shadow-lg">
             <button
               type="button"
               onClick={() => onReply(message.id)}
-              className="font-sans text-[10px] font-bold uppercase tracking-wider text-muted-foreground hover:text-primary min-w-[44px] min-h-[44px] md:min-w-0 md:min-h-0 flex items-center justify-center"
+              className="px-2 py-1 text-xs text-muted-foreground hover:text-primary hover:bg-muted/50 transition-colors"
+              title="Reply"
             >
-              Reply
+              ↩
             </button>
-            {!isDeleted && message.user.username === currentUsername && (
+            {message.user.username === currentUsername && (
               <button
                 type="button"
                 onClick={() => onDelete(message.channel_id, message.id)}
-                className="font-sans text-[10px] font-bold uppercase tracking-wider text-muted-foreground hover:text-destructive min-w-[44px] min-h-[44px] md:min-w-0 md:min-h-0 flex items-center justify-center"
+                className="px-2 py-1 text-xs text-muted-foreground hover:text-destructive hover:bg-destructive/10 transition-colors border-l-2 border-border"
+                title="Delete"
               >
-                Del
+                ×
               </button>
             )}
           </div>
-        </div>
+        )}
 
         {/* Content */}
         <div className={cn(