feat: add Data Engineering Agent A2A client example [2/2]

[xtan999]

Description

Adds a sample Python client implementation using the Agent-to-Agent (A2A) protocol to interact with the Google Cloud Data Engineering Agent.

Key features:

• A2A SDK integration for discovery and client creation.
• ADC authentication support.
• Multi-turn conversation state persistence via local tokens.
• Handling of DEADLINE_EXCEEDED with automated resumption.
• Support for custom agent instructions.

Fixes #14252

Checklist

Testing

• [ x] I have tested this change on a live environment and verified it works as intended.

Compliance & Style

• [x ] I have followed the Sample Guidelines.
• [ x] The README is updated with all relevant information (if applicable).
• [ x] If this PR adds a new sample directory: I updated the CODEOWNERS file.

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Post-Approval Actions

• [ x] Please merge this PR for me once it is approved

[gemini-code-assist]

Code Review

This pull request introduces a sample Python client for the Google Cloud Data Engineering Agent (DEA) using the Agent-to-Agent (A2A) protocol, complete with documentation and unit tests. The client supports session persistence, custom instruction loading, and automated resumption on deadline exceeded. The reviewer provided valuable feedback to improve the robustness of the implementation, including correcting the return type annotation of the main interaction function, implementing a retry limit to prevent infinite loops during repeated deadline exceeded errors, and handling potential file reading errors and hidden files when loading instructions.

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• geminidataanalytics/dataengineeringagent/dea_a2a_client.py:122, tag geminidataanalytics_a2a_client

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[saurabh-net]

LGTM