fix: Pi harness - dynamic models, correct RPC protocol, proper event handling

Backend:
- /api/pi/models now calls 'pi --list-models' with stored API keys
- pi-bridge.ts: callback-based event handling (matches pi-monorepo)
- pi-bridge.ts: correct RPC format (type: 'prompt' not jsonrpc)
- pi-bridge.ts: pass API keys to Pi process env
- websocket.ts: event handler runs in background, no blocking
- rest.ts: fix user home path (getHomeDir instead of hardcoded)

Frontend:
- Fix /api/ double prefix in useChatSessions, useChatGroups, useModels
- Add PROVIDER_DISPLAY mapping in SystemSettings.tsx
- Provider tabs show friendly names (e.g., 'OpenCode Zen')

UI (from previous session):
- Grouped session list with collapsible folders
- CreateGroupDialog, GroupContextMenu, SessionContextMenu components

src/apps/officer-web/state/useModels.ts

@@ -18,7 +18,7 @@ export function usePiModels() {
     queryKey: ['PI_MODELS'],
     enabled: isAuthenticated,
     queryFn: async () => {
-      const data = await client.get<{ models: ModelOption[] }>('/api/pi/models');
+      const data = await client.get<{ models: ModelOption[] }>('/pi/models');
       return data.models;
     },
     staleTime: 5 * 60 * 1000,