Run command, offloading large output to a file in the sandbox.
Captures the command's combined output: returned inline when it is at or
below max_inline_bytes, otherwise left at capture_path (so the caller
can surface a read_file pointer) with only a head/tail preview returned.
Captured output is hard-capped at max_capture_bytes (default
_EXECUTE_CAPTURE_MAX_BYTES) without killing the command, so the exit
code is preserved. When enable_capture_offload is False, the command
runs unwrapped and the full output is returned (offloaded=False), so
callers can fall back to their own handling (e.g. generic eviction).
