isSyntheticUserText function
Whether a user-role text is synthetic harness content (system-notice envelope, agent mail, or a projected branch summary) rather than the user's own words. Shared by the summarizer's request-candidate scan and the structured compaction ledger (which must never hide a real user turn).
Implementation
bool isSyntheticUserText(String text) =>
_systemNoticePattern.hasMatch(text) ||
_branchSummaryPattern.hasMatch(text) ||
_agentMailPattern.hasMatch(text);