Handle stdin-stream control-flow errors gracefully

[cte]

Summary

• add a shared expected-control-flow error classifier for stdin stream mode
• treat abort/cancel variants, no-active-task cancel races, and stream teardown-on-shutdown as non-fatal control flow
• apply classifier in both CLI runtime unhandled error handlers and stdin-stream client/cancel paths
• add focused unit tests for new classifiers and contexts

Interactively review PR in Roo Code Cloud