docs: add Auto Agent Protocol and Lumika to partners list

[yankouskia]

Closes #1908

Adds two entries to the partners list:

• Auto Agent Protocol — an A2A vertical.
• Lumika — partner actively promoting A2A and its integration into car dealership websites.

Related articles

• https://autoagentprotocol.org/
• https://lumika.ai/a2a
• https://lumika.ai/articles/auto-agent-protocol-1-0-connecting-1000-dealerships-free
• https://lumika.ai/articles/what-if-your-ai-could-actually-buy-you-a-car
• https://medium.com/@alex_21933/a2a-the-quiet-protocol-that-lets-anything-talk-to-anything-ff6ac7a56482
• https://medium.com/@alex_21933/auto-agent-protocol-hits-1-0-and-were-connecting-1-000-dealerships-for-free-5e2021837501
• https://medium.com/@alex_21933/what-if-your-ai-could-actually-buy-you-a-car-7ba84bae4a55

[gemini-code-assist]

Code Review

This pull request adds 'Auto Agent Protocol' to the partners list in docs/partners.md. The reviewer suggested sorting the list alphabetically by placing 'Auto Agent Protocol' before 'Autodesk'.

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[msampathkumar]

Thank you for your work @yankouskia @AndreiMisiukevich

If possible I request you join our next meeting to share more details on why/how A2A helped you. You can find details at https://github.com/a2aproject/A2A/blob/main/GOVERNANCE.md#tsc-meetings

[yankouskia]

@msampathkumar will be there, thank you!