fix: refine preview switching logic and fix code generation prompt

Author: AshishKumar4

src/routes/chat/chat.tsx

@@ -482,7 +482,10 @@ export default function Chat() {
 			hasSeenPreview.current = true;
 		} else if (previewUrl) {
 			const isExistingChat = urlChatId !== 'new';
-			const shouldSwitch = behaviorType === 'agentic' || isPhase1Complete || isExistingChat;
+			const shouldSwitch =
+				behaviorType === 'agentic' ||
+				(behaviorType === 'phasic' && isPhase1Complete) ||
+				(isExistingChat && behaviorType !== 'phasic');
 
 			if (shouldSwitch) {
 				setView('preview');

worker/agents/operations/SimpleCodeGeneration.ts

@@ -33,8 +33,6 @@ Your task is to generate production-ready code files specifically based on the p
 ## Critical Guidelines
 - Write clean, type-safe TypeScript code
 - Follow best practices for the specific project type
-- For Workflows: use WorkflowEntrypoint, step.do(), step.sleep() patterns
-- For Workers: use standard Worker patterns with Request/Response
 - Ensure all imports are correct
 - Add proper error handling
 - Include JSDoc comments where helpful