Avoid overflow in remote read bounds checks

[fallintoplace]

Summary

• avoid overflow in remote read bounds checks by comparing file_offset before subtracting from _nbytes
• use the same bounds helper in direct RemoteHandle::read() and the MULTI_POLL pread() setup path
• add a regression test for a wrapping file_offset + size range that must fail before range setup

Validation

• pre-commit run --files cpp/src/remote_handle.cpp cpp/tests/test_remote_handle.cpp
• git diff --check

Not run locally: ci/run_ctests.sh -R REMOTE_HANDLE_TEST because no installed/devcontainer KvikIO test build was present at the paths searched by the script.

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[vuule]

/ok to test 3ebae94

[vyasr]

Needs style fixes before CI can run properly.