Complete frontend migration to unified Pi harness (Phase 7 + Phase 9)

- Delete legacy hooks: useClaude.ts, useOpenCode.ts, usePiMono.ts, App.backup.tsx
- Update all components to use usePi instead of legacy hooks
- Replace useVisiblePiMonoModels/useClaudeModels/useOpenCodeModels with useVisiblePiModels
- Migrate from LegacyChatMessage to ChatMessage type throughout
- Update SessionBar to remove provider and archive props
- Simplify ChatDetailPanel to Pi-only (remove Claude/OpenCode components)
- Fix useChatSessions calls (remove provider parameter)
- Update user-settings types: provider now only 'pi' instead of legacy values
- Update PI_HARNESS_REBUILD.md to mark phases complete

src/apps/officer-web/Screens/Dashboard/Home/ChatLauncher.tsx

@@ -23,7 +23,7 @@ import {
   DropdownMenuTrigger,
 } from '@/components/ui/dropdown-menu';
 import { useSettings } from '@/state/useSettings';
-import { useVisiblePiMonoModels } from '@/state/useModels';
+import { useVisiblePiModels, type ModelOption } from '@/state/useModels';
 import type { Attachment } from '@/Screens/Dashboard/Chat/EmbeddableChat';
 
 const PROVIDER_DISPLAY: Record<string, string> = {
@@ -46,7 +46,7 @@ const PROVIDER_DISPLAY: Record<string, string> = {
 export const ChatLauncher = () => {
   const navigate = useNavigate();
   const { settings } = useSettings();
-  const piMonoModels = useVisiblePiMonoModels();
+  const piModels = useVisiblePiModels();
 
   const client = useClient();
   const [model, setModel] = useState<string | null>(settings.chat.defaultModel);
@@ -62,17 +62,17 @@ export const ChatLauncher = () => {
   }, [settings.chat.defaultModel]);
 
   const providers = useMemo(
-    () => [...new Set(piMonoModels.map((m) => m.provider).filter(Boolean))] as string[],
-    [piMonoModels],
+    () => [...new Set(piModels.map((m: ModelOption) => m.provider).filter(Boolean))] as string[],
+    [piModels],
   );
 
-  const activeProvider = piMonoModels.find((m) => m.id === model)?.provider ?? providers[0];
-  const providerModels = piMonoModels.filter((m) => m.provider === activeProvider);
+  const activeProvider = piModels.find((m: ModelOption) => m.id === model)?.provider ?? providers[0];
+  const providerModels = piModels.filter((m: ModelOption) => m.provider === activeProvider);
 
   const displayName = (provider: string) => PROVIDER_DISPLAY[provider] ?? provider;
 
   const handleProviderClick = (provider: string) => {
-    const firstModel = piMonoModels.find((m) => m.provider === provider);
+    const firstModel = piModels.find((m: ModelOption) => m.provider === provider);
     if (firstModel) setModel(firstModel.id);
   };