Adds the canonical ADR referenced by build.cfg and the consolidation work
(from docs/adr-agent-harness-consolidation, which merges clean). Prepends a
dated Update note: the ADR's "remove Pi" guidance is superseded — Pi is DEMOTED
to a spawnable backend (kept on-image, Node stays), zot is the primary harness,
per docs/COLIBRI-JAILED-AGENT-SPAWN-DESIGN.md. Original record preserved.
Co-authored-by: Sam & Claude (original ADR)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
