Adds two design RFCs under docs/rfcs/ authored by MS-LEAD for the
Mosaic Stack comms-evolution program (sponsor/veto: Jason). RFC-001
is the MACP architecture (self-hosted Synapse + Mosaic appservice,
protocol, presence/escalation, federation, strangler migration off
Hermes). RFC-002 is the open-source install/config/topology substrate
RFC-001's phases run on. Docs only, no code. Links added to
docs/SITEMAP.md.
