chore: import upstream snapshot with attribution

contributing/samples/workflows/retry/README.md

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+# ADK Workflow Sample: Node Retries
+
+## Overview
+
+In real-world applications, interacting with external APIs, databases, or third-party services can occasionally result in transient failures (e.g., temporary network outages, rate limits, or bad gateways).
+
+The ADK framework allows you to easily handle these scenarios by wrapping the unreliable logic in a `@node` decorator configured with `RetryConfig`. If the node raises one of the expected exceptions, the workflow engine automatically pauses, waits for a backoff delay, and reschedules the node for another attempt.
+
+When a node raises an exception, the framework automatically emits an error event (with `error_code` and `error_message`) so the error is visible in the event stream. If the node has retry configured, it will be retried after the backoff delay.
+
+This sample demonstrates a `get_weather` node that intentionally fails randomly (70% chance) by raising an `HTTPError` representing a 500 Internal Server error. The framework gracefully recovers and eventually succeeds, passing the result to `report_weather`.
+
+## Graph
+
+```mermaid
+graph TD
+    START --> get_weather[get_weather <br/>Retries on HTTPError]
+    get_weather --> report_weather
+```
+
+## How To
+
+1. **Import `RetryConfig`**: Ensure you import the configuration class to set your retry parameters.
+
+   ```python
+   from google.adk.workflow import RetryConfig
+   ```
+
+1. **Configure the Decorator**: Apply the `@node` decorator to your Python function and specify the `retry_config` parameter with your desired logic (e.g., `max_attempts`, `initial_delay`).
+
+   ```python
+   @node(retry_config=RetryConfig(max_attempts=5, initial_delay=1))
+   def get_weather(ctx: Context) -> str:
+       # ... flaky logic here ...
+   ```
+
+   When an exception like `HTTPError` occurs, the ADK framework catches it, emits an error event, and processes the backoff delay automatically. As long as `max_attempts` hasn't been exceeded, the node executes again.
+
+1. **Track Retries (Optional)**: If you need to know which attempt the node is currently running, you can access `ctx.attempt_count` from the `Context`.
+
+   ```python
+   yield Event(message=f"Getting weather... attempt {ctx.attempt_count}")
+   ```