Improper Python sample codes and API mismatches in graph workflow documentation

**Describe the bug**

Multiple Python sample codes across the Graph Workflows documentation (`docs/graphs/`) contain code discrepancies, syntax errors, and API mismatches with the surrounding explanatory text and the ADK Python 2.0 runtime:

1. **`docs/graphs/routes.md` (Loop and escalation exit)**:
- The section describes creating iterative loops with back-edges and exit termination routes in a `Workflow`. However, the Python code snippet is an exact duplicate of the forward branching router and contains **no loop, no back-edge, and no exit condition**.

2. **`docs/graphs/human-input.md` (Tool-confirmation: approval prompts in LLM agents)**:
- The text explicitly introduces LLM agent-level **Tool Confirmation** (`FunctionTool` / `tool_context.request_confirmation`) and contrasts it with standalone graph HITL nodes. However, the Python sample code shows an `initial_prompt` workflow function node yielding `RequestInput`, which is a graph-level HITL pause rather than tool confirmation.

3. **`docs/graphs/data-handling.md` (Access structured data in agents)**:
- The text and code introduce an imaginary angle-bracket syntax (``) that does not exist in ADK Python. Furthermore, `START` is unquoted and unimported, and `city_generator_agent` is referenced without definition.

4. **`docs/graphs/dynamic.md` (Loop route)**:
- The `code_workflow` function contains both `yield Event(...)` and `return code` within an `async def`, causing Python to raise a `SyntaxError: 'return' with value in async generator`. It is also missing `rerun_on_resume=True`.

5. **`docs/graphs/dynamic.md` (Nodes / FunctionNode wrapper)**:
- `FunctionNode(my_function_node, ...)` passes the function positionally, but `FunctionNode.__init__` enforces keyword-only arguments (`def __init__(self, *, func: Callable, ...)`), raising a `TypeError` at runtime.

6. **`docs/graphs/data-handling.md` (Session state and state scopes)**:
- Omitted necessary imports (`Context`, `Event`, `Workflow`, `Content`), causing `NameError` when executing the snippet.

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**To Reproduce**

Steps to reproduce the behavior:
1. Navigate to the following documentation pages:
- `docs/graphs/routes.md#loop-and-escalation-exit`
- `docs/graphs/human-input.md#tool-confirmation-approval-prompts-in-llm-agents`
- `docs/graphs/data-handling.md#access-structured-data-in-agents`
- `docs/graphs/dynamic.md#loop-route`
- `docs/graphs/dynamic.md#node`
2. Compare the code samples with the surrounding text descriptions and run the sample codes in a standard ADK Python 2.0 environment.
3. Observe syntax errors (`SyntaxError`), runtime exceptions (`TypeError`, `NameError`), and functional mismatches with the text.

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**Expected behavior**

1. `routes.md` should demonstrate an actual loop workflow with a back-edge and terminal route.
2. `human-input.md` should demonstrate static and dynamic tool confirmation (`FunctionTool(..., require_confirmation=True)` and `tool_context.request_confirmation(...)`).
3. `data-handling.md` should demonstrate standard structured data input schemas (`input_schema=CityTime`) with valid prompt instructions without phantom syntax.
4. `dynamic.md` should demonstrate a valid programmatic `while` loop that returns the result cleanly without mixing generator `yield` and `return value` in the same function, and include `rerun_on_resume=True`.
5. `dynamic.md` should use keyword arguments for `FunctionNode(func=...)`.
6. All snippets should be self-contained with complete imports.

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**Screenshots**

*N/A (Code and documentation issue)*

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**Versions**

- OS: macOS / Linux / Windows
- ADK version: 2.0.0
- Python version: 3.10+

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**Additional context**

A complete patch fixing all 6 issues is prepared as attachment

[fix-graphs-docs-code-samples.patch](https://github.com/user-attachments/files/31341857/fix-graphs-docs-code-samples.patch)

Start with the six affected sections in docs/graphs/routes.md, human-input.md, data-handling.md, and dynamic.md, then compare each sample with the surrounding text and the attached patch. Run the snippets in a standard ADK Python 2.0 environment; done means the examples match their explanations, use valid APIs and imports, and execute without the reported syntax or runtime errors.

Written by the indexing model from the issue text.