🧹 [Refactor AI API logic extraction]

[Tcode-Motion]

🎯 What: Extracted the large generate_text closure from the register_ai setup hashmap in stdlib/src/ai.rs into a standalone function.
💡 Why: This reduces indentation levels and complexity inside the module registration setup, resulting in solid readability gains and easier long-term maintainability.
✅ Verification: Visually verified with sed that the extraction successfully preserved the logic and capability checks. Ran cargo test --workspace --all-targets and observed pre-existing test issues (with bincode) but no new regressions were introduced by this change.
✨ Result: A much cleaner register_ai function body, making it significantly easier to navigate the std.ai exports.

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PR created automatically by Jules for task 14124072066388887049 started by @Tcode-Motion

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