docs(health): align shared-contract to shipped API + per-lib CLAUDE.md + cleanup

- Contract: DatabaseHealthCheck<TContext> ctor now shows IServiceProvider (resolves
  IDbContextFactory<TContext> when registered, else a scoped TContext; pool-safe)
- Contract: RequireActiveNode gains retryAfterSeconds = 5 default parameter
- Packages: remove dangling AspNetCore.HealthChecks.UI.Client PackageVersion (no
  csproj referenced it)
- Tests: fix CS8625 in RoleLessCases — use object?[] so null role rows compile
  warning-free under Nullable=enable
- Add ZB.MOM.WW.Health/CLAUDE.md (packages, responsibilities, consumer matrix,
  build/test/pack commands, status + pointer to components/health/)

ZB.MOM.WW.Health/tests/ZB.MOM.WW.Health.Akka.Tests/ActiveNodeDecisionTests.cs

@@ -14,12 +14,12 @@ namespace ZB.MOM.WW.Health.Akka.Tests;
 public sealed class ActiveNodeDecisionTests
 {
     // Role-less: requiredRole == null. hasRole is irrelevant. Healthy iff (selfUp && isLeader), else Unhealthy.
-    public static IEnumerable<object[]> RoleLessCases() => new[]
+    public static IEnumerable<object?[]> RoleLessCases() => new[]
     {
-        new object[] { true, true, false, (string?)null, HealthStatus.Healthy },
-        new object[] { true, false, false, (string?)null, HealthStatus.Unhealthy },
-        new object[] { false, true, false, (string?)null, HealthStatus.Unhealthy },
-        new object[] { false, false, false, (string?)null, HealthStatus.Unhealthy },
+        new object?[] { true, true, false, (string?)null, HealthStatus.Healthy },
+        new object?[] { true, false, false, (string?)null, HealthStatus.Unhealthy },
+        new object?[] { false, true, false, (string?)null, HealthStatus.Unhealthy },
+        new object?[] { false, false, false, (string?)null, HealthStatus.Unhealthy },
     };
 
     [Theory]