LineIterator hangs forever if the streamed response ends without a trailing newline

[RudraDudhat2509]

LineIterator.__next__ hangs forever if the last chunk of a streamed response has no trailing newline.

sagemaker-core/src/sagemaker/core/iterators.py:

except StopIteration:
    if self.read_pos < self.buffer.getbuffer().nbytes:
        continue
    raise

continue re-reads the same unterminated line, fails the same check, calls next() on the now-exhausted byte_iterator again, gets StopIteration again, forever. Nothing in that branch changes read_pos or the buffer.

Repro:

from sagemaker.core.iterators import LineIterator

chunks = [
    {"PayloadPart": {"Bytes": b'{"outputs": [" a"]}\n'}},
    {"PayloadPart": {"Bytes": b'{"outputs": [" b"]}'}},
]

for line in LineIterator(iter(chunks)):
    print(line)

Prints the first line then hangs.

Will open a PR.