refactor(core): centralize OpenAI usage via call_ai()

[Alokbpandey]

• I understand that this repository is auto-generated and my pull request may not be merged

Changes being requested

Refactored all example usages to use a single call_ai() function wrapper for better code reuse and maintainability.

Updates include:

• Introduced call_ai() helper to simplify calling Chat Completion API
• Read OPENAI_API_KEY securely from environment variables using os.environ.get
• Replaced repeated client.chat.completions.create() calls with call_ai()
• Updated both text-based and image-based (vision) prompt examples

Additional context & links

This is a code quality improvement to make example usage cleaner and safer, especially for developers who copy-paste from docs.

While I understand this repo is auto-generated and not meant to be manually edited, I'm sharing this in case it's helpful or influences future generation.

GitHub profile: @Alokbpandey