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/TaskLogs/index.tsx

@@ -2,7 +2,7 @@ import { useState, useEffect } from 'react';
 import { Search, AlertCircle, CheckCircle2, Clock, ArrowLeft } from 'lucide-react';
 import { useClient } from 'hooks/useClient';
 import { Card } from '@/components/Card';
-import { MessageBubble, type LegacyChatMessage } from 'apps/Chat';
+import { MessageBubble, type ChatMessage } from 'apps/Chat';
 
 type LogMetadata = {
   filename: string;
@@ -18,7 +18,7 @@ type LogMetadata = {
 };
 
 type FullLog = LogMetadata & {
-  messages: LegacyChatMessage[];
+  messages: ChatMessage[];
 };
 
 const formatDate = (iso: string) => {