ConfigureLogging is now idempotent via a _loggingConfigured guard field so
repeated calls from subclasses do not abandon and leak the previous logger.
The previous Log.Logger is disposed before overwriting to release its
console-sink resources cleanly.
A new protected static FlushLogging() helper calls Log.CloseAndFlush() so
commands can guarantee buffered output is flushed in their finally blocks
before the process exits — important for the long-running subscribe verb.
XML doc updated to reflect call-once semantics and document FlushLogging().
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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