Name the medium Ichor and scaffold it in Pony at src/ichor:
- Envelope {source,dest,provenance,payload} mirroring Ada Organ_Message
- Broker actor: register + perfusion route; Brain-bound traffic crosses D1
- Barrier (D1) admit: Pony provenance-law mirror + Ada FFI seam sketched
- StubOrgan + main smoke wiring (deliver internal, reject external)
- ichor_ada_shim.c: C/Fortran binding seam to Ada Trust_Guard (stub)
Not compiled in-env (no ponyc). Updates D2 spec to SCAFFOLD/Pony.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015hmgREHNsxYCuim33yUF2c
