Extract shared code patterns

Identify and extract duplicate code patterns into shared utility functions to improve maintainability and reduce redundancy. When similar logic appears in multiple places, create a reusable function in a shared utility file.

Example of problematic code:

// In openai.ts
private isInsufficientQuotaError(error: any): boolean {
    // Duplicate quota detection logic
}

// In openai-compatible.ts
private isInsufficientQuotaError(error: any): boolean {
    // Same quota detection logic repeated
}

Better approach:

// In shared/quota-utils.ts
export function isInsufficientQuotaError(error: any): boolean {
    // Centralized quota detection logic
}

// In both files:
import { isInsufficientQuotaError } from '../shared/quota-utils';

Key guidelines:

• Look for repeated logic patterns across files
• Extract shared functionality into well-named utility functions
• Place utilities in appropriate shared locations
• Document the purpose and usage of shared utilities
• Consider making utilities generic enough for reuse but specific enough to maintain clear purpose

This improves code maintainability by:

• Reducing duplicate code that needs to be maintained
• Centralizing logic for easier updates
• Making the codebase more DRY (Don’t Repeat Yourself)
• Improving testability of shared functionality