docs: add Grinta to AI and Agents

[josephsenior]

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• PR title format: Add project-name
• Entry format: - [project-name](url) - Description ending with period.
• Description is concise and short

Why This Project Is Awesome

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• Industry Standard - The go-to tool for a specific use case
• Rising Star - 5000+ stars in < 2 years, significant adoption
• Hidden Gem - Exceptional quality, solves niche problems elegantly

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How It Differs

If similar entries exist, what makes this one unique?

[Copilot]

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[JinyangWang27]

Please make sure the git diff shows only one new line

[JinyangWang27]

Thanks for your submission. However, this project does not meet our acceptance criteria:

GitHub stars: 0 stars (minimum 100 required, or strong justification for Hidden Gem).
Uniqueness: no explanation for what makes this project different from the others.

Please see our CONTRIBUTING.md for full requirements. You're welcome to resubmit once the project has matured and gained community traction.