loadbearer v0.4.0

• Two new CPU subtests: AES-256-GCM and SHA-256 throughput. These pick up
  the CPU's AES-NI / CLMUL / SHA hardware where present (detected at runtime),
  so a chip that lacks crypto acceleration — common before ~2019 — now shows up
  in the grade. Adds the aes-gcm and sha2 crates.
• New memory subtest: Sequential read, all cores. The other bandwidth
  subtests are single-threaded; this one runs the read kernel on every logical
  CPU and sums the rates, capturing whether the memory subsystem scales past
  one or two cores (many dual-channel laptops don't).
• reference-v1 gains cpu/aes_gcm, cpu/sha256 and memory/bw_read_mt
  anchors (provisional, like the rest).
• Because these join the CPU and memory geometric means, scores shift for
  machines that lack crypto acceleration or don't scale memory bandwidth.

Full Changelog: v0.3.1...v0.4.0