The includeStacktrace parameter was working backwards - when false,
it would return the full message with embedded stack traces, and when
true, it would extract the stack trace but the logic was inverted.
Changes:
- Always extract the first line as the message text
- Only populate stackTrace field when includeStacktrace is true
- Ensures clean, summary-only messages when includeStacktrace is false
- Properly separates stack traces into their own field when requested
This matches the expected Unity console behavior where the summary
is shown by default, and stack traces are only shown when expanded.
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