Add Google ADK (Gemini) agent samples

[maxjneto]

What was changed

Added google_adk/ — a new sample directory demonstrating the newest temporalio[google-adk] integration with Google's Agent Development Kit (Gemini models).

Three sub-examples:

• basic/ — Hello world agent + activity-backed tools via activity_tool
• orchestration/ — Sequential pipeline, parallel fan-out, and iterative loop patterns
• human_in_the_loop/ — Signal-based approval before sensitive tool execution

Also updated:

• pyproject.toml — added google-adk dependency group
• README.md — added google_adk to the samples list

Why?

The openai_agents/ sample demonstrates the OpenAI Agents SDK integration, but there's no equivalent for the Google ADK integration (temporalio.contrib.google_adk_agents). This fills that gap, showing users how to use TemporalModel, activity_tool, GoogleAdkPlugin, and workflow primitives (signals, queries) with ADK agents.

Checklist

1. Closes no existing issue, happy to open one if preferred

2. How was this tested:

   • uv run ruff check google_adk/ — passes
   • uv run ruff format --check google_adk/ — passes
   • uv run mypy --check-untyped-defs --namespace-packages google_adk/ — passes (0 errors, 19 files)
   • Manual run with local Temporal server + GOOGLE_API_KEY set:

     uv sync --group google-adk
     # Terminal 1
     uv run google_adk/basic/run_worker.py
     # Terminal 2
     uv run google_adk/basic/run_hello_world_workflow.py
     

3. Any docs updates needed?

   • README in google_adk/README.md is included with full instructions
   • Root README.md updated with one-line listing
   • No docs.temporal.io changes needed unless the team wants to link to it from the google-adk contrib module docs

[CLAassistant]

All committers have signed the CLA.

[DABH]

Hey @maxjneto , thanks so much for your contribution! We added some Google ADK samples in our repository https://github.com/temporalio/samples-python/tree/main/google_adk_agents that appear to subsume what is in this PR, so we will close this PR for now. But if there are any gaps you still notice or any other samples you'd like to see, please let us know / feel free to re-open or open a new PR. Thanks again!