Refactor A2UI extension activation

[nan-yu]

The agents may support multiple versions of A2UI extensions. Based on client requested extension, the agent SDK should dynamically activate one that is supported by the agent.

Screenshots of the custom components in contact_multiple_surfaces sample

• Org chart and contact card:

• Floor plan:

• Message:

There is an (empty) block on the UI, but it sounds like a client renderer issue.

Screenshots of the rizzcharts components:

• 

Fixes: flutter/genui#821

Description

Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.

List which issues are fixed by this PR. For larger changes, raising an issue first helps reduce redundant work.

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

[nan-yu]

I've got the contact_lookup, restaurant_finder and rizzcharts samples working individually, but when testing the orchestrator sample, the A2UI extension seems not to be propagated to the sub agents. I'll take a deeper look later and verify other samples, component_gallery and mcp_app_proxy.

[nan-yu]

Verified the following samples

• contact_lookup
• restaurant_finder
• rizzcharts
• orchestrator
• component_gallery
• mcp_app_proxy

[wrenj]

I've got the contact_lookup, restaurant_finder and rizzcharts samples working individually, but when testing the orchestrator sample, the A2UI extension seems not to be propagated to the sub agents. I'll take a deeper look later and verify other samples, component_gallery and mcp_app_proxy.

fyi the code the orchestrator subagent extension activation is here
https://github.com/google/A2UI/blob/main/samples/agent/adk/orchestrator/agent.py#L67

it's pretty janky but thats the best we could do with the existing sdk

[nan-yu]

I've got the contact_lookup, restaurant_finder and rizzcharts samples working individually, but when testing the orchestrator sample, the A2UI extension seems not to be propagated to the sub agents. I'll take a deeper look later and verify other samples, component_gallery and mcp_app_proxy.

fyi the code the orchestrator subagent extension activation is here https://github.com/google/A2UI/blob/main/samples/agent/adk/orchestrator/agent.py#L67

it's pretty janky but thats the best we could do with the existing sdk

Thanks for the pointer. I've got the orchestrator sample working last night by injecting the correct A2UI_EXTENSION_URI. All samples are working now.

[dmandar]

Overall looks good. thx for doing this. Can we add screenshots showing the 3 custom components working for posterity? (contact org, card and location). Please also make sure clicking works in each.

[jacobsimionato]

Wow, thanks for doing this so fast!

[dmandar]

LGTM, pls add screenshots

[nan-yu]

Screenshots added to the PR description. Merging now.