chore: add OV-1 hero + avatar in paper palette

Andrew Dunnrequested to merge
andunn-iconography into main

Adds hero.svg + avatar.svg per the lab tidy-skill iconography spec. Hero is the 4-column OV-1 of the build pipeline (upstream + patches -> matrix -> attest -> tags). Avatar shows image-layer stack with attestation footer. README gains the hero at the top.

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