Make streaming implementation trio-compatible (#84)

## Summary
- Replace asyncio.create_task() with anyio task group for trio
compatibility
- Update client.py docstring example to use anyio.sleep
- Add trio example demonstrating multi-turn conversation

## Details
The SDK already uses anyio for most async operations, but one line was
using asyncio.create_task() which broke trio compatibility. This PR
fixes that by using anyio's task group API with proper lifecycle
management.

### Changes:
1. **subprocess_cli.py**: Replace asyncio.create_task() with anyio task
group, ensuring proper cleanup on disconnect
2. **client.py**: Update docstring example to use anyio.sleep instead of
asyncio.sleep
3. **streaming_mode_trio.py**: Add new example showing how to use the
SDK with trio

## Test plan
- [x] All existing tests pass
- [x] Manually tested with trio runtime (created test script that
successfully runs multi-turn conversation)
- [x] Linting and type checking pass

🤖 Generated with [Claude Code](https://claude.ai/code)

examples/streaming_mode_trio.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+"""
+Example of multi-turn conversation using trio with the Claude SDK.
+
+This demonstrates how to use the ClaudeSDKClient with trio for interactive,
+stateful conversations where you can send follow-up messages based on
+Claude's responses.
+"""
+
+import trio
+
+from claude_code_sdk import (
+    AssistantMessage,
+    ClaudeCodeOptions,
+    ClaudeSDKClient,
+    ResultMessage,
+    SystemMessage,
+    TextBlock,
+    UserMessage,
+)
+
+
+def display_message(msg):
+    """Standardized message display function.
+
+    - UserMessage: "User: <content>"
+    - AssistantMessage: "Claude: <content>"
+    - SystemMessage: ignored
+    - ResultMessage: "Result ended" + cost if available
+    """
+    if isinstance(msg, UserMessage):
+        for block in msg.content:
+            if isinstance(block, TextBlock):
+                print(f"User: {block.text}")
+    elif isinstance(msg, AssistantMessage):
+        for block in msg.content:
+            if isinstance(block, TextBlock):
+                print(f"Claude: {block.text}")
+    elif isinstance(msg, SystemMessage):
+        # Ignore system messages
+        pass
+    elif isinstance(msg, ResultMessage):
+        print("Result ended")
+
+
+async def multi_turn_conversation():
+    """Example of a multi-turn conversation using trio."""
+    async with ClaudeSDKClient(
+        options=ClaudeCodeOptions(model="claude-3-5-sonnet-20241022")
+    ) as client:
+        print("=== Multi-turn Conversation with Trio ===\n")
+
+        # First turn: Simple math question
+        print("User: What's 15 + 27?")
+        await client.query("What's 15 + 27?")
+
+        async for message in client.receive_response():
+            display_message(message)
+        print()
+
+        # Second turn: Follow-up calculation
+        print("User: Now multiply that result by 2")
+        await client.query("Now multiply that result by 2")
+
+        async for message in client.receive_response():
+            display_message(message)
+        print()
+
+        # Third turn: One more operation
+        print("User: Divide that by 7 and round to 2 decimal places")
+        await client.query("Divide that by 7 and round to 2 decimal places")
+
+        async for message in client.receive_response():
+            display_message(message)
+
+        print("\nConversation complete!")
+
+
+if __name__ == "__main__":
+    trio.run(multi_turn_conversation)

src/claude_code_sdk/_internal/transport/subprocess_cli.py

@@ -45,6 +45,7 @@ class SubprocessCLITransport(Transport):
         self._pending_control_responses: dict[str, dict[str, Any]] = {}
         self._request_counter = 0
         self._close_stdin_after_prompt = close_stdin_after_prompt
+        self._task_group: anyio.abc.TaskGroup | None = None
 
     def _find_cli(self) -> str:
         """Find Claude Code CLI binary."""
@@ -160,9 +161,9 @@ class SubprocessCLITransport(Transport):
                 if self._process.stdin:
                     self._stdin_stream = TextSendStream(self._process.stdin)
                     # Start streaming messages to stdin in background
-                    import asyncio
-
-                    asyncio.create_task(self._stream_to_stdin())
+                    self._task_group = anyio.create_task_group()
+                    await self._task_group.__aenter__()
+                    self._task_group.start_soon(self._stream_to_stdin)
             else:
                 # String mode: close stdin immediately (backward compatible)
                 if self._process.stdin:
@@ -183,6 +184,12 @@ class SubprocessCLITransport(Transport):
         if not self._process:
             return
 
+        # Cancel task group if it exists
+        if self._task_group:
+            self._task_group.cancel_scope.cancel()
+            await self._task_group.__aexit__(None, None, None)
+            self._task_group = None
+
         if self._process.returncode is None:
             try:
                 self._process.terminate()

src/claude_code_sdk/client.py

@@ -63,7 +63,7 @@ class ClaudeSDKClient:
             await client.query("Count to 1000")
 
             # Interrupt after 2 seconds
-            await asyncio.sleep(2)
+            await anyio.sleep(2)
             await client.interrupt()
 
             # Send new instruction