Ge a2ui v09 examples

[yuantian-agentspace]

Description

Gemini Enterprise A2UI v0.9 demo agent to demo GE's capabilities to render Material components and custom components.

Demo agent for Gemini Enterprise.

Pre-launch Checklist

One time:

• I signed the CLA.
• I read the Contributors Guide.
• I read the Style Guide.
• I have built and run at least one sample.

For this PR:

• I have updated the relevant CHANGELOG.md file.
• I updated/added relevant documentation.
• My code changes (if any) have tests.
• If my branch is on a 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 introduces a new demo agent sample for A2UI v0.9, showcasing Material and custom components with deployment configurations, example templates, and a restaurant finder tool. The review feedback highlights several critical stability and maintainability improvements: adding defensive type-checking in agent_executor.py and tools.py to prevent AttributeError crashes from unexpected client payloads, correcting the Python version requirement in pyproject.toml and README.md from the unreleased 3.14 to >=3.11, and moving the token_stream helper function in agent.py outside of the retry loop to avoid redundant recreation.

[ditman]

@yuantian-agentspace @suyangw-g this landed with a broken test:

• https://github.com/a2ui-project/a2ui/actions/runs/30111246916/job/89541023835
• https://github.com/a2ui-project/a2ui/actions/runs/30110989291/job/89540163036

(Which is now failing on main)

Do you mind taking a look?