6a4fa220de
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.