feat(graph): add support for agent node interrupts

[pgrayy]

Motivation

Users configuring Agent instances with interrupt capabilities (via tool_context.interrupt()) currently cannot use them within Graph execution. When an Agent node raises an interrupt, the Graph throws a NotImplementedError. This PR enables Graph to handle agent node interrupts, following the pattern established in the Swarm implementation.

Resolves: #1526

Public API Changes

No public API changes. Graph now properly handles interrupts from Agent nodes using the existing tool_context.interrupt() API:

from strands import Agent, tool
from strands.multiagent import GraphBuilder
from strands.multiagent.base import Status
from strands.types.tools import ToolContext

@tool(name="weather_tool", context=True)
def weather_tool(tool_context: ToolContext) -> str:
    response = tool_context.interrupt("weather_approval", reason="need location")
    return f"Weather in {response}: sunny"

weather_agent = Agent(name="weather", tools=[weather_tool])

builder = GraphBuilder()
builder.add_node(weather_agent, "weather_agent")
graph = builder.build()

# First invocation - will be interrupted
result = graph("What is the weather?")
assert result.status == Status.INTERRUPTED
assert len(result.interrupts) == 1

# Resume with response
responses = [{"interruptResponse": {"interruptId": result.interrupts[0].id, "response": "Seattle"}}]
result = graph(responses)
assert result.status == Status.COMPLETED

Use Cases

• Human-in-the-loop workflows: Agent nodes can pause for human approval before proceeding with sensitive operations
• Interactive data collection: Agents can request additional information from users mid-execution
• Parallel execution with selective interrupts: When multiple nodes run in parallel, non-interrupted nodes complete normally while interrupted nodes wait for responses

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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