DO NOT MERGE Contains indexer scaling poc schooltimetabling

[ge0ffrey]

School timetabling scheduling POC benchmark of contains vs filtering
From 9236/sec to 22056/sec on only 100 entities.

Before

Constraint softTagOld(ConstraintFactory constraintFactory) {
    // A teacher prefers to teach sequential lessons and dislikes gaps between lessons.
    return constraintFactory
            .forEach(Lesson.class)
            .join(Lesson.class, Joiners.filtering((a, b) -> a.getTags().contains(b.getReqTag())))
            .reward(HardSoftScore.ONE_SOFT)
            .asConstraint("Soft tag");
}

2026-01-02 17:31:42,151 INFO Problem scale: entity count (100), variable count (200), approximate value count (31), approximate problem scale (4.065119 × 10^217).
2026-01-02 17:31:42,416 INFO Construction Heuristic phase (0) ended: time spent (267), best score (-6hard/5946soft), move evaluation speed (56818/sec), step total (100).
2026-01-02 17:32:12,154 INFO Local Search phase (1) ended: time spent (30005), best score (-4hard/5946soft), move evaluation speed (8815/sec), step total (41832).
2026-01-02 17:32:12,156 INFO Solving ended: time spent (30007), best score (-4hard/5946soft), move evaluation speed (9236/sec), phase total (2), environment mode (PHASE_ASSERT), move thread count (NONE).

After

Constraint softTagNew(ConstraintFactory constraintFactory) {
    // A teacher prefers to teach sequential lessons and dislikes gaps between lessons.
    return constraintFactory
            .forEach(Lesson.class)
            .join(Lesson.class, Joiners.contain(Lesson::getTags, Lesson::getReqTag))
            .reward(HardSoftScore.ONE_SOFT)
            .asConstraint("Soft tag");
}

2026-01-02 17:32:46,053 INFO Problem scale: entity count (100), variable count (200), approximate value count (31), approximate problem scale (4.065119 × 10^217).
2026-01-02 17:32:46,284 INFO Construction Heuristic phase (0) ended: time spent (233), best score (-6hard/5946soft), move evaluation speed (65217/sec), step total (100).
2026-01-02 17:33:16,057 INFO Local Search phase (1) ended: time spent (30006), best score (-4hard/5946soft), move evaluation speed (21727/sec), step total (103137).
2026-01-02 17:33:16,059 INFO Solving ended: time spent (30008), best score (-4hard/5946soft), move evaluation speed (22056/sec), phase total (2), environment mode (PHASE_ASSERT), move thread count (NONE).