classifyStepTargets function

@visibleForTesting ({List<HintStep> deferred, List<UnknownHintTarget> typos}) classifyStepTargets(HintTour tour, Set<String> knownIds)

Classifies a tour's steps by their targetId against the registry's known ids.

Typo policy:

• a step with candidates (similar ids exist) — a typo: fails loudly in debug, is skipped in release (waiting for it is pointless);
• a step without candidates — a legitimate deferred target: wait, the timeout produces its own diagnosis;
• a step whose only difference from a candidate is digits (target1/target2 sequences) — also deferred: numeric suffixes are naming, not typos; otherwise every following step in a sequence would look like a typo of the previous one. A pure function: tested directly, applied by the controller.

Implementation

@visibleForTesting
({List<HintStep> deferred, List<UnknownHintTarget> typos}) classifyStepTargets(
    HintTour tour, Set<String> knownIds) {
  final deferred = <HintStep>[];
  final typos = <UnknownHintTarget>[];
  for (var i = 0; i < tour.steps.length; i++) {
    final step = tour.steps[i];
    if (knownIds.contains(step.targetId)) continue;
    final candidates = closestTargetIds(step.targetId, knownIds);
    if (candidates.isEmpty ||
        _differsOnlyInDigits(step.targetId, candidates.first)) {
      deferred.add(step);
    } else {
      typos.add((step: step, index: i, candidates: candidates));
    }
  }
  return (deferred: deferred, typos: typos);
}