chore: import upstream snapshot with attribution

contributing/samples/workflows/state/README.md

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+# ADK Workflow State Sample
+
+## Overview
+
+This sample demonstrates different ways to manage state in an **ADK Workflow**. State is a dictionary shared across all nodes in the workflow execution, useful for gathering information across multiple steps without passing everything directly from one node's output to another's input.
+
+In this sample, we show four techniques:
+
+1. Updating state via direct dictionary mutation: `ctx.state["key"] = "value"`
+1. Updating state by yielding an event: `yield Event(state={"key": "value"})`
+1. Reading state via direct dictionary access: `ctx.state["key"]`
+1. Reading state via automatic parameter injection: `def func(key: str): ...`
+
+## Sample Inputs
+
+- `Hello ADK!`
+
+- `Testing state management.`
+
+## Graph
+
+```mermaid
+graph TD
+    START --> process_initial_input
+    process_initial_input --> update_state_via_event
+    update_state_via_event --> read_state_via_ctx
+    read_state_via_ctx --> read_state_via_param
+```
+
+## How To
+
+1. **Update state via direct mutation:** Access the context and modify `ctx.state` directly.
+
+   ```python
+   def process_initial_input(ctx, node_input: str):
+       ctx.state["original_text"] = node_input
+   ```
+
+1. **Update state via Event:** Yield an `Event` object with a `state` delta dictionary.
+
+   ```python
+   def update_state_via_event(node_input: str):
+       yield Event(
+           state={"uppercased_text": node_input.upper()}
+       )
+   ```
+
+1. **Read state via context:** Retrieve values from `ctx.state`.
+
+   ```python
+   def read_state_via_ctx(ctx):
+       original = ctx.state["original_text"]
+   ```
+
+1. **Read state via parameter injection:** Declare a function parameter that matches the key in the workflow state, and ADK will automatically populate it.
+
+   ```python
+   def read_state_via_param(appended_text: str):
+       return f"Final Result: {appended_text}!"
+   ```