chat: rename usePiChat → useChat, PiMonoInner → AgenticTaskRunner

Frontend de-Pi (Stage 3). Renames the chat hook usePiChat → useChat (+ UsePiChatType
→ UseChatType, file moved to hooks/useChat.ts) across all consumers, and renames
the TaskRunnerModal agentic runner PiMonoInner → AgenticTaskRunner (dropping the
dead defaultProvider === 'pi' check → always the Claude default). Pure rename, no
behavior change. The WS route stays /api/pi/chat/ws until Stage 4.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/apps/officer-web/Screens/Dashboard/CapabilityPage.tsx

@@ -9,7 +9,7 @@ import { Button } from '@/components/ui/button';
 import { Dialog, DialogContent, DialogHeader, DialogTitle, DialogDescription } from '@/components/ui/dialog';
 import { useClient } from 'hooks/useClient';
 import { Card } from '@/components/Card';
-import { usePiChat, EmbeddableChat } from 'officerdev';
+import { useChat, EmbeddableChat } from 'officerdev';
 type CapabilitySummary = {
   dirName: string;
   name: string;
@@ -279,7 +279,7 @@ export const CapabilityChat = ({
     ? (description ?? `Help me create the content for this new ${kind} file`)
     : `Help me understand and improve this ${kind} file`;
 
-  const pi = usePiChat(undefined, undefined, { replaceUrl: false });
+  const pi = useChat(undefined, undefined, { replaceUrl: false });
 
   const onResponseEndRef = useRef(onResponseEnd);
   onResponseEndRef.current = onResponseEnd;