SEP-1686: Tasks (#1645)

examples/clients/simple-task-interactive-client/README.md

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+# Simple Interactive Task Client
+
+A minimal MCP client demonstrating responses to interactive tasks (elicitation and sampling).
+
+## Running
+
+First, start the interactive task server in another terminal:
+
+```bash
+cd examples/servers/simple-task-interactive
+uv run mcp-simple-task-interactive
+```
+
+Then run the client:
+
+```bash
+cd examples/clients/simple-task-interactive-client
+uv run mcp-simple-task-interactive-client
+```
+
+Use `--url` to connect to a different server.
+
+## What it does
+
+1. Connects to the server via streamable HTTP
+2. Calls `confirm_delete` - server asks for confirmation, client responds via terminal
+3. Calls `write_haiku` - server requests LLM completion, client returns a hardcoded haiku
+
+## Key concepts
+
+### Elicitation callback
+
+```python
+async def elicitation_callback(context, params) -> ElicitResult:
+    # Handle user input request from server
+    return ElicitResult(action="accept", content={"confirm": True})
+```
+
+### Sampling callback
+
+```python
+async def sampling_callback(context, params) -> CreateMessageResult:
+    # Handle LLM completion request from server
+    return CreateMessageResult(model="...", role="assistant", content=...)
+```
+
+### Using call_tool_as_task
+
+```python
+# Call a tool as a task (returns immediately with task reference)
+result = await session.experimental.call_tool_as_task("tool_name", {"arg": "value"})
+task_id = result.task.taskId
+
+# Get result - this delivers elicitation/sampling requests and blocks until complete
+final = await session.experimental.get_task_result(task_id, CallToolResult)
+```
+
+**Important**: The `get_task_result()` call is what triggers the delivery of elicitation
+and sampling requests to your callbacks. It blocks until the task completes and returns
+the final result.
+
+## Expected output
+
+```text
+Available tools: ['confirm_delete', 'write_haiku']
+
+--- Demo 1: Elicitation ---
+Calling confirm_delete tool...
+Task created: <task-id>
+
+[Elicitation] Server asks: Are you sure you want to delete 'important.txt'?
+Your response (y/n): y
+[Elicitation] Responding with: confirm=True
+Result: Deleted 'important.txt'
+
+--- Demo 2: Sampling ---
+Calling write_haiku tool...
+Task created: <task-id>
+
+[Sampling] Server requests LLM completion for: Write a haiku about autumn leaves
+[Sampling] Responding with haiku
+Result:
+Haiku:
+Cherry blossoms fall
+Softly on the quiet pond
+Spring whispers goodbye
+```