Rewrites the active-node sections of the spec and shared contract, which
described the leader-based design that both consumers rejected.
- SPEC §2.3 replaced: the rule, the ordered RolePreference, why a node holding
none of the preferred roles is Unhealthy rather than Healthy, and the data
payload. §4 (IActiveNodeGate) and the tier table follow.
- SPEC §6 marked historical: it still tells adopters to use
ActiveNodeHealthCheck(role: "admin") and AkkaActiveNodeGate, which is the
advice that produced the defect. Kept for provenance, annotated so nobody
follows it again.
- GAPS: gaps L1/L2 recorded as closed the wrong way, reopened, then closed at
0.3.0 — including the part worth remembering, that both apps adopted the
shared check as specified, hit it live, and reverted to private copies, so the
surface reached zero consumers by being avoided rather than unused.
- Index rows updated with the consumer-visible changes and both app branches.