fix: address CodeRabbitAI review comments for conversation history

- Fix duplicate onConversationCreated callbacks by tracking activeConversationId
- Fix history loss when switching conversations with Map-based deduplication
- Disable input while conversation is loading to prevent message routing issues
- Gate WebSocket debug logs behind DEV flag (import.meta.env.DEV)
- Downgrade server logging from info to debug level for reduced noise
- Fix .gitignore prefixes for playwright paths (ui/playwright-report/, ui/test-results/)
- Remove debug console.log from ConversationHistory.tsx
- Add staleTime (30s) to single conversation query for better caching
- Increase history message cap from 20 to 35 for better context
- Replace fixed timeouts with condition-based waits in e2e tests

ui/src/hooks/useConversations.ts

@@ -25,6 +25,7 @@ export function useConversation(projectName: string | null, conversationId: numb
     queryKey: ['conversation', projectName, conversationId],
     queryFn: () => api.getAssistantConversation(projectName!, conversationId!),
     enabled: !!projectName && !!conversationId,
+    staleTime: 30_000, // Cache for 30 seconds
   })
 }