add end of command options to sanitize user prompt (#130)

The PR should address the issue where user prompt maybe treated as a
option with leading `-`
Assuming `claude` does follow POSIX standard, the `--` option should
solve the issue.

fixes #129

Author: 8519mark

src/claude_code_sdk/_internal/transport/subprocess_cli.py

@@ -157,7 +157,7 @@ def _build_command(self) -> list[str]:
             cmd.extend(["--input-format", "stream-json"])
         else:
             # String mode: use --print with the prompt
-            cmd.extend(["--print", str(self._prompt)])
+            cmd.extend(["--print", "--", str(self._prompt)])
 
         return cmd