probeExistence

private fn

void probeExistence(bool  csr,  Tables)(Tables tables,  size_t mask,
       const  ArrayData[][]  lkeyChunks,  const  size_t[]  lstarts,
       const  size_t[]  lHashes,  const  ArrayData[][]  rkeyChunks,
       const  size_t[]  rstarts,  const  ColumnEq[]  eqs,
       JoinKind kind,  size_t segLen,  size_t nSegs,  size_t lheight,
       size_t[][]  segKeep)

The existence probe of SEMI/ANTI (ADR-2026-10-23-07): fixed left-row segments over the immutable table, each filling its kept left rows

SEMI keeps rows with at least one match, ANTI the rest (null-key rows never match, so ANTI keeps them). Left order, at most one output row per left row, the left schema unchanged.