docs: add AGenUI v0.9 renderer to ecosystem

[niuma-zb]

Description

Adding AGenUI/AGenUI to the community renderers list.

• Platform: iOS, Android, HarmonyOS
• Protocol: A2UI v0.9
• Extends A2UI protocol with a Styles property for richer component appearance and layout control
• Basic Catalog components + 4 built-in extensions (Table, Carousel, Web, RichText)
• Custom component registration API
• Custom Function Call registration API
• Progressive rendering as LLM tokens arrive
• Freestanding Catalog JSON Schema for agent negotiation
• Bundled A2UI Generation Skill for LLM agents

Pre-launch Checklist

• I signed the CLA.
• I read the Contributors Guide.
• I read the Style Guide.
• I have added updates to the CHANGELOG.
• I updated/added relevant documentation.
• My code changes (if any) have tests.
• If my branch is on fork, I have verified that scripts/e2e_test.sh passes.

If you need help, consider asking for advice on the discussion board.

[gemini-code-assist]

Code Review

This pull request adds the AGenUI renderer to the ecosystem documentation, including a new entry in the renderers table and a detailed description in the notable mentions section. Feedback identifies a typo in the platform name ('HarmoryOS' instead of 'HarmonyOS') and requests formatting adjustments to the table and description paragraph to ensure consistency with the repository's style guide.