Split good and bad captures in move ordering

[KnightStackSys]

Updates the isolated move-ordering experiment with a more conservative 4PC capture split.

Ordering policy

• TT move remains first
• terminal king captures remain ahead of normal moves
• promotions remain ahead of ordinary captures
• checking captures are always kept in the high tactical ordering band
• ordinary captures with SEE >= -150 remain ahead of quiet moves
• only captures with SEE < -150 are moved below quiet-history moves
• capture history still refines ordering within capture groups
• quiet checks, countermoves, quiet history, and continuation history are otherwise unchanged

Rationale

The original SEE >= 0 split tested poorly. In 4PC, slightly negative SEE captures can still be tactically important because multiple players move before an exchange fully resolves. This revision only demotes clearly bad captures and explicitly preserves checking captures.

Scope

• only src/search.cpp changes
• no changes to PVS, LMR, LMP, SEE pruning, TT policy, history updates, MDP, aspiration windows, or evaluation

Restart the SPRT against current main; prior results from the old SEE >= 0 version should not be mixed with this revision.