fix(desktop): component cleanup + dead code removal + DeerFlow ai-elements

- ChatArea: DeerFlow ai-elements annotations for accessibility
- Conversation: remove unused Context, simplify message rendering
- Delete dead modules: audit-logger.ts, gateway-reconnect.ts
- Replace console.log with structured logger across components
- Add idb dependency for IndexedDB persistence
- Fix kernel-skills type safety improvements

desktop/src/components/ai/Conversation.tsx

@@ -1,41 +1,4 @@
-import { useRef, useEffect, useState, createContext, useContext, useMemo, type ReactNode } from 'react';
-
-// ---------------------------------------------------------------------------
-// ConversationContext — shared state for child ai-elements components
-// ---------------------------------------------------------------------------
-
-interface ConversationContextValue {
-  isStreaming: boolean;
-  setIsStreaming: (v: boolean) => void;
-  messages: unknown[];
-  setMessages: (msgs: unknown[]) => void;
-}
-
-const ConversationContext = createContext<ConversationContextValue | null>(null);
-
-export function useConversationContext() {
-  const ctx = useContext(ConversationContext);
-  if (!ctx) {
-    throw new Error('useConversationContext must be used within ConversationProvider');
-  }
-  return ctx;
-}
-
-export function ConversationProvider({ children }: { children: ReactNode }) {
-  const [isStreaming, setIsStreaming] = useState(false);
-  const [messages, setMessages] = useState<unknown[]>([]);
-
-  const value = useMemo(
-    () => ({ isStreaming, setIsStreaming, messages, setMessages }),
-    [isStreaming, messages],
-  );
-
-  return (
-    <ConversationContext.Provider value={value}>
-      {children}
-    </ConversationContext.Provider>
-  );
-}
+import { useRef, useEffect, type ReactNode } from 'react';
 
 // ---------------------------------------------------------------------------
 // Conversation container with auto-stick-to-bottom scroll behavior

desktop/src/components/ai/index.ts

@@ -1,4 +1,4 @@
-export { Conversation, ConversationProvider, useConversationContext } from './Conversation';
+export { Conversation } from './Conversation';
 export { ReasoningBlock } from './ReasoningBlock';
 export { StreamingText } from './StreamingText';
 export { ChatMode, type ChatModeType, type ChatModeConfig, CHAT_MODES } from './ChatMode';