README

Architecture notes and design documents.

The canonical port-from-SSD assessment will land here as SSD_PORT_ASSESSMENT.md (generated in parallel by the W1.1 sibling agent). When present, that file enumerates every source under the upstream SSD checkout, classifies it by port target (sim/, bridge/, rl/, perception/, trajectory_db/, schema/, profiles/, assets/), and is the authority for what later waves move into this package.