isMinimalSession function
Check if a session is minimal (warmup only).
Implementation
bool isMinimalSession(String sessionId, Map<String, SessionFacets> facets) {
final sessionFacets = facets[sessionId];
if (sessionFacets == null) return false;
final cats = sessionFacets.goalCategories;
final catKeys = cats.entries
.where((e) => e.value > 0)
.map((e) => e.key)
.toList();
return catKeys.length == 1 && catKeys.first == 'warmup_minimal';
}