Add healResetIncarnation (federationReset.ts): fires from onPeerActivated after
an authenticated re-peer to soft-tombstone the flagged pure S2S stubs of a reset
peer's dead incarnation, clearing stale friendships/DMs so the reported bug is
fixed. Two mandatory guards: a reason gate (allow-list of 8 genuine handshake
activation reasons; excludes health_check_recovery + startup_bootstrap so their
stale baseline can never silently resolve a journal without healing) and an
epoch comparison (dead_epoch === newEpoch => false alarm, no tombstone). Uses
tombstoneUser(uid, { purgeContent: false }); real federated accounts are left
flagged + intact for Phase 2. Runs outside any transaction. Wire into
onPeerActivated before the mutation-log re-sync.
Jannis Braun