Add stdio regression test for raw invalid UTF-8 tool arguments

[raashish1601]

Summary

• add an end-to-end stdio regression for issue [Bug] Server crashes with anyio.ClosedResourceError when receiving raw invalid UTF-8 bytes #2328 using raw invalid UTF-8 bytes in a tools/call request
• assert the server returns a JSON-RPC error response instead of crashing or dropping the reply on stdin EOF
• exercise the existing stdio transport plus low-level server path without external server packages

Testing

• PYTHONPATH=src python -m pytest -o addopts='' tests/issues/test_2328_stdio_invalid_utf8.py -q
• PYTHONPATH=src python -m pytest -o addopts='' tests/server/test_stdio.py tests/issues/test_2328_stdio_invalid_utf8.py -q
• python -m ruff check tests/issues/test_2328_stdio_invalid_utf8.py
• git diff --check

[maxisbey]

Thanks for the PR. This has since landed via #2306. Closing as part of a general backlog cleanup ahead of the v2 release. If this is still relevant against current main, feel free to reopen.

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