Adds 'Peer Activation Recovery' subsection with call-site roster,
peer-state x outbox-enqueue x recovery matrix, mutation log
coverage table, /api/federation/sync contextType filter values,
and a Known Issues note about the poison-pill edge case.
Also updates stale references to runInitialSyncForNewPeers (removed
in commit 02a1ed7) to point at the unified startupBootstrapSync
path.