### wai-quantum 0.6.8: threads only where they pay, and a cut-rank search that recounts only what moved

Additive. No result changes a bit: every kernel path gives the same bits at any thread count,
and every pinned digest is unchanged.

- **State-vector passes** (`quantum_sv`): a gate, a slice pass or a fixed-chunk sum now spawns
  at most one thread per `2¹⁸` amplitudes. Each pass spawns its threads afresh, and below
  that size a thread costs more than its share. On a shared 32-core host, a gate from 14 to
  18 qubits ran 5 to 14 times slower with a thread per core than on one thread. A count that a
  test forces is still taken as it is, so the split paths stay tested at small sizes. The
  ignored `gate_timings` test prints the times.
- **The cut-rank search** (`ProductMeasured::anneal_order`) moves one qubit at a time. Seven
  moves in eight go at most four places, and the rest anywhere. Only the cuts between the
  two places are recounted, so a move costs about a ninth of a full recount. On the 70-qubit
  graph-state circuit, 300 000 moves reach a 29-bit widest cut in about six seconds. In
  tests, every move's recounted cuts are checked against a full recount.
- **The service's `cutrank` method:**
  - The planner makes one short search, enough to bound the job's memory and work.
  - The run searches up to 300 000 moves from each of four seeds, on threads of their own,
    with the planner's order among the candidates.
  - It keeps the cheapest order whose widest cut is no wider than the planner's, so a job
    stays inside the memory it was admitted with.

