Fix KeyError and async cleanup issues

- Fix KeyError for 'cost_usd' by using .get() with fallback to 'total_cost'
- Handle GeneratorExit exception during async cleanup
- Add try/except for cancel_scope.cancel() to prevent RuntimeError

These changes resolve runtime errors when using the SDK with Claude Code CLI.

src/claude_code_sdk/_internal/client.py

@@ -86,13 +86,13 @@ class InternalClient:
                 # Map total_cost to total_cost_usd for consistency
                 return ResultMessage(
                     subtype=data["subtype"],
-                    cost_usd=data["cost_usd"],
+                    cost_usd=data.get("cost_usd", data.get("total_cost", 0.0)),
                     duration_ms=data["duration_ms"],
                     duration_api_ms=data["duration_api_ms"],
                     is_error=data["is_error"],
                     num_turns=data["num_turns"],
                     session_id=data["session_id"],
-                    total_cost_usd=data["total_cost"],
+                    total_cost_usd=data.get("total_cost", 0.0),
                     usage=data.get("usage"),
                     result=data.get("result"),
                 )

src/claude_code_sdk/_internal/transport/subprocess_cli.py

@@ -196,10 +196,15 @@ class SubprocessCLITransport(Transport):
                             raise SDKJSONDecodeError(line_str, e) from e
                         continue
 
-            except anyio.ClosedResourceError:
+            except (anyio.ClosedResourceError, GeneratorExit):
                 pass
             finally:
-                tg.cancel_scope.cancel()
+                # Cancel the task group gracefully
+                try:
+                    tg.cancel_scope.cancel()
+                except RuntimeError:
+                    # Ignore errors if cancel scope is already exited
+                    pass
 
         await self._process.wait()
         if self._process.returncode is not None and self._process.returncode != 0: