Enable partial support for MacOS/MPS training - #626

these 18 derivations will be built:
  /nix/store/znghiypg0jacdh2cgwhbks7fvdhvdk0n-psyche-sidecar-0.2.0.drv
  /nix/store/97k1szzdi4i6lizh3hjbnjg30kzpgyks-psyche-sidecar.drv
  /nix/store/l4qsbaphhanm9ypa5z1b6asba5ni1n8l-psyche-sidecar-nixgl-wrapped.drv
  /nix/store/d1yszhycs6yflqsb8qbf4cwfzxnn42yj-psyche-centralized-client-0.2.0.drv
  /nix/store/rjwjsdsrhhgms029c198r3f3gbhw6p5y-psyche-centralized-client.drv
  /nix/store/vfdk6b8vl9wkrq2glkiy7z7c46flcs98-psyche-centralized-client-nixgl-wrapped.drv
  /nix/store/6l11xw80n028xyph9xkps4kglql5ab2b-psyche-solana-client-0.2.0.drv
  /nix/store/6qq14bnrpqn4pdla2bj17xm6z1z7x8n9-psyche-solana-client.drv
  /nix/store/z55sb21x28vcnrzm84rakcz1hw9aj5mn-psyche-solana-client-nixgl-wrapped.drv
  /nix/store/85pszhy1gbgfjh29acqcgfzwny4xd7dp-psyche-book.drv
  /nix/store/2iyv88z3lhxgc7xs80a8758kcfz55d4y-Caddyfile.drv
  /nix/store/39za7yyfmq3frhnid0ah6zsyv8p95jdy-Caddyfile-formatted.drv
  /nix/store/8yrwnmgpvxpxsd5178phqi58dxvaigvg-X-Reload-Triggers-caddy.drv
  /nix/store/h64dick6n63p6hwvqbq7j8mpag4d405p-unit-caddy.service.drv
  /nix/store/v6xh607mjxz9an501k0xwjlp6xwc5ig8-system-units.drv
  /nix/store/bvhnpsg1wm1a97cbwy5xjxzrxlprxqz7-etc.drv
  /nix/store/l6pjr6fj7p529kjjmhqrh1cpw9ywsd5l-activate.drv
  /nix/store/cggxap7rb6ziiwiyvygx14gl25znz89a-nixos-system-nixos-26.05.20260121.88d3861.drv
these 2 paths will be fetched (6.97 MiB download, 29.33 MiB unpacked):
  /nix/store/6nklr5p6sa5mnmms4qy13njiif3zgkc1-psyche-centralized-local-testnet-0.2.0
  /nix/store/rl7nxmdnwiliqbp4rg7yvkgzbqp6w5f0-psyche-centralized-server-0.2.0