feat: Add prompt enhancement feature and English UI localization

[lgd-matlab]

Overview

This PR adds a custom prompt enhancement feature and converts Chinese UI text to English in the Advanced Settings section.

Features Added

• ✨ Custom Prompt Enhancement: Users can now define custom instruction templates to optimize their prompts
• 🔧 Flexible Placeholder Support: Supports multiple placeholder formats including {prompt}, {history}, {context}, {{prompt}}, {{history}}, {{context}}
• 🤖 AI-Powered Optimization: Uses the same AI model as the current chat to enhance prompts
• 📝 Context Integration: Incorporates conversation history and additional context into prompt optimization

Technical Implementation

• New File: src/promptEnhancer.ts - Core prompt enhancement logic
• Enhanced Settings: Updated Advanced Settings UI with English text
• Template System: Supports custom instruction templates with variable substitution
• Error Handling: Comprehensive error handling and result validation
• Type Safety: Full TypeScript support with proper interfaces

Changes Made

Core Files

• src/promptEnhancer.ts - New prompt enhancement engine
• src/settings/v2/components/AdvancedSettings.tsx - UI localization to English
• src/settings/model.ts - Settings model updates
• src/constants.ts - Added necessary constants
• src/components/Chat.tsx - Integration with chat functionality
• src/components/chat-components/ChatInput.tsx - Input handling updates

Key Features

1. Prompt Type Detection: Automatically detects prompt types (content generation, analysis, Q&A, format conversion)
2. Multi-format Placeholder Support:
   • {prompt} / {original_prompt} - Original user prompt
   • {history} / {chat_history} - Conversation history
   • {context} / {added_context} - Additional context
   • Double brace variants: {{prompt}}, {{history}}, {{context}}
3. Smart Result Cleaning: Removes AI response prefixes and validates output
4. Fallback Mechanism: Returns original prompt if enhancement fails

Code Quality

• ✅ Passes ESLint checks
• ✅ TypeScript strict mode compliant
• ✅ Comprehensive error handling
• ✅ Detailed logging for debugging
• ✅ Clean code architecture with separation of concerns

Usage Example

Users can now set custom enhancement templates like:
You are an expert prompt engineer. Enhance the following prompt:

Original: {prompt}
Context: {context}
History: {history}

Make it more specific and actionable.

Testing

• Code passes all lint checks
• TypeScript compilation successful
• UI text properly localized to English
• Placeholder substitution working correctly
• Error handling tested

Breaking Changes

None - This is a purely additive feature that doesn't affect existing functionality.

Screenshots

(Add screenshots of the English UI if available)

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This enhancement significantly improves the user experience by providing intelligent prompt optimization while maintaining a clean, English-language interface.