fix: TS build errors — remove asChild, simplify type selector

- SheetTrigger: remove asChild (base-ui doesn't support it)
- ComposeBox: use plain buttons with cn() instead of ToggleGroup (API mismatch)
- Remove unused Button import from App

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

ui/colony/src/App.tsx

@@ -6,7 +6,6 @@ import { ChannelSidebar } from "@/components/ChannelSidebar";
 import { MessageItem } from "@/components/MessageItem";
 import { ComposeBox } from "@/components/ComposeBox";
 import { Sheet, SheetContent, SheetTrigger } from "@/components/ui/sheet";
-import { Button } from "@/components/ui/button";
 
 export default function App() {
   const [channels, setChannels] = useState<Channel[]>([]);
@@ -87,10 +86,8 @@ export default function App() {
         <div className="px-3 py-2 md:px-4 border-b border-border flex items-center gap-2">
           {/* Mobile: Sheet trigger */}
           <Sheet open={sheetOpen} onOpenChange={setSheetOpen}>
-            <SheetTrigger asChild>
-              <Button variant="ghost" size="sm" className="md:hidden p-1 h-8 w-8 text-muted-foreground">
-                =
-              </Button>
+            <SheetTrigger className="md:hidden p-1 h-8 w-8 text-muted-foreground hover:text-foreground rounded-sm">
+              =
             </SheetTrigger>
             <SheetContent side="left" className="p-0 w-64 bg-background">
               {sidebar}