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/CapabilityPage.tsx

@@ -8,9 +8,9 @@ import { ArrowLeft, Pencil, Plus, Check, X, Trash2, Search, ChevronRight } from
 import { Button } from '@/components/ui/button';
 import { Dialog, DialogContent, DialogHeader, DialogTitle, DialogDescription } from '@/components/ui/dialog';
 import { useClient } from 'hooks/useClient';
-import { useVisiblePiMonoModels } from '@/state/useModels';
+import { useVisiblePiModels } from '@/state/useModels';
 import { Card } from '@/components/Card';
-import { usePiMono } from '@/Screens/Dashboard/Chat/usePiMono';
+import { usePi } from '@/Screens/Dashboard/Chat/usePi';
 import { EmbeddableChat } from '@/Screens/Dashboard/Chat/EmbeddableChat';
 type CapabilitySummary = {
   dirName: string;
@@ -64,30 +64,30 @@ export const CapabilityChat = ({
   description,
   onResponseEnd,
 }: CapabilityChatProps) => {
-  const piMonoModels = useVisiblePiMonoModels();
+  const piModels = useVisiblePiModels();
   const seedFile = `${kind.toUpperCase()}.md`;
   const promptFrontmatter = `<frontmatter>\ninput file: ${filePath}\n${seedFile}: ${filePath}\ndir: ${resourceDir}\n\nBe aware of any extra files alongside the same dir as the ${kind} file we're handling, for possible extra context. You can also, if pertinent, create scripts or other files that will help you in the future.\n</frontmatter>`;
   const defaultInput = isNew
     ? description ?? `Help me create the content for this new ${kind} file`
     : `Help me understand and improve this ${kind} file`;
 
-  const piMono = usePiMono(undefined, undefined, { replaceUrl: false });
+  const pi = usePi(undefined, undefined, { replaceUrl: false });
 
   const onResponseEndRef = useRef(onResponseEnd);
   onResponseEndRef.current = onResponseEnd;
 
   const wasGenerating = useRef(false);
   useEffect(() => {
-    if (wasGenerating.current && !piMono.isGenerating) {
+    if (wasGenerating.current && !pi.isGenerating) {
       onResponseEndRef.current?.();
     }
-    wasGenerating.current = piMono.isGenerating;
-  }, [piMono.isGenerating]);
+    wasGenerating.current = pi.isGenerating;
+  }, [pi.isGenerating]);
 
   return (
     <EmbeddableChat
-      chat={piMono}
-      availableModels={piMonoModels}
+      chat={pi}
+      availableModels={piModels}
       defaultInput={defaultInput}
       promptPrefix={promptFrontmatter}
       className="h-full"