Moved to docs/architecture.md — the Agent OS kernel / layered model (Trust Model, Mail Bridge, isolation strategies, state persistence) is the single authority for TPS's architecture.
For the wire-protocol detail of remote Branch Offices specifically (Noise_IK handshake, SSH-tunnel transport, provisioning), see docs/branch-office.md. For design rationale — why TPS is built this way — see DESIGN.md.