Prevent recursive standard output logging

[AvdLee]

Summary

• stop replaying captured stdout/stderr after the original output destination fails
• avoid writing replay errors back into the captured streams
• continue persisting captured output to the diagnostics log
• add regression coverage for a closed output destination

Root cause

A detached long-running app could lose its original terminal. FileHandle.write then raised an Objective-C exception, and the catch block used print, feeding the error back into the captured pipe indefinitely.

Testing

• swift test (57 tests passed)