test: use context manager for read session in test_stream_ops

[quettabit]

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[quettabit]

@greptileai review pls

[greptile-apps]

Greptile Summary

This PR updates the stream operation tests for the ReadSession lifecycle.

• Uses ReadSession as an async context manager.
• Preserves bounded reads, tailing timeouts, and error assertions.
• Ensures sessions close after completion, cancellation, or failure.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
tests/test_stream_ops.py	Updates read-session tests to enter and close sessions through the async context-manager API.

_{Reviews (2): Last reviewed commit: "initial commit" | Re-trigger Greptile}