Phase 6.2 Stream B — permission-trie evaluator in Core.Authorization

Ships Stream B.1-B.6 — the data-plane authorization engine Phase 6.2 runs on.
Integration into OPC UA dispatch (Stream C — Read / Write / HistoryRead /
Subscribe / Browse / Call etc.) is the next PR on this branch.

New Core.Abstractions:
- OpcUaOperation enum enumerates every OPC UA surface the evaluator gates:
  Browse, Read, WriteOperate/Tune/Configure (split by SecurityClassification),
  HistoryRead, HistoryUpdate, CreateMonitoredItems, TransferSubscriptions,
  Call, AlarmAcknowledge/Confirm/Shelve. Stream C maps each one back to its
  dispatch call site.

New Core.Authorization namespace:
- NodeScope record + NodeHierarchyKind — 6-level scope addressing for
  Equipment-kind (UNS) namespaces, folder-segment walk for SystemPlatform-kind
  (Galaxy). NodeScope carries a Kind selector so the evaluator knows which
  hierarchy to descend.
- AuthorizationDecision { Verdict, Provenance } + AuthorizationVerdict
  {Allow, NotGranted, Denied} + MatchedGrant. Tri-state per decision #149;
  Phase 6.2 only produces Allow + NotGranted, Denied stays reserved for v2.1
  Explicit Deny without API break.
- IPermissionEvaluator.Authorize(session, operation, scope).
- PermissionTrie + PermissionTrieNode + TrieGrant. In-memory trie keyed on
  the ACL scope hierarchy. CollectMatches walks Cluster → Namespace →
  UnsArea → UnsLine → Equipment → Tag (or → FolderSegment(s) → Tag on
  Galaxy). Pure additive union — matches that share an LDAP group with the
  session contribute flags; OR across levels.
- PermissionTrieBuilder static factory. Build(clusterId, generationId, rows,
  scopePaths?) returns a trie for one generation. Cross-cluster rows are
  filtered out so the trie is cluster-coherent. Stream C follow-up wires a
  real scopePaths lookup from the live DB; tests supply hand-built paths.
- PermissionTrieCache — process-singleton, keyed on (ClusterId, GenerationId).
  Install(trie) adds a generation + promotes to "current" when the id is
  highest-known (handles out-of-order installs gracefully). Prior generations
  retained so an in-flight request against a prior trie still succeeds; GC
  via Prune(cluster, keepLatest).
- UserAuthorizationState — per-session cache of resolved LDAP groups +
  AuthGenerationId + MembershipVersion + MembershipResolvedUtc. Bounded by
  MembershipFreshnessInterval (default 15 min per decision #151) +
  AuthCacheMaxStaleness (default 5 min per decision #152).
- TriePermissionEvaluator — default IPermissionEvaluator. Fails closed on
  stale sessions (IsStale check short-circuits to NotGranted), on cross-
  cluster requests, on empty trie cache. Maps OpcUaOperation → NodePermissions
  via MapOperationToPermission (total — every enum value has a mapping; tested).

Tests (27 new, all pass):
- PermissionTrieTests (7): cluster-level grant cascades to every tag;
  equipment-level grant doesn't leak to sibling equipment; multi-group union
  ORs flags; no-matching-group returns empty; Galaxy folder-segment grant
  doesn't leak to sibling folder; cross-cluster rows don't land in this
  cluster's trie; build is idempotent (B.6 invariants).
- TriePermissionEvaluatorTests (8): allow when flag matches; NotGranted when
  no matching group; NotGranted when flags insufficient; HistoryRead requires
  its own bit (decision-level requirement); cross-cluster session denied;
  stale session fails closed; no cached trie denied; MapOperationToPermission
  is total across every OpcUaOperation.
- PermissionTrieCacheTests (8): empty cache returns null; install-then-get
  round-trips; new generation becomes current; out-of-order install doesn't
  downgrade current; invalidate drops one cluster; prune retains most recent;
  prune no-op when fewer than keep; cluster isolation.
- UserAuthorizationStateTests (4): fresh is not stale; IsStale after 5 min
  default; NeedsRefresh true between freshness + staleness windows.

Full solution dotnet test: 1078 passing (baseline 906, Phase 6.1 = 1042,
Phase 6.2 Stream A = +9, Stream B = +27 = 1078). Pre-existing Client.CLI
Subscribe flake unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Core/Authorization/AuthorizationDecision.cs

@@ -0,0 +1,48 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
+
+namespace ZB.MOM.WW.OtOpcUa.Core.Authorization;
+
+/// <summary>
+///     Tri-state result of an <see cref="IPermissionEvaluator.Authorize"/> call, per decision
+///     #149. Phase 6.2 only produces <see cref="AuthorizationVerdict.Allow"/> and
+///     <see cref="AuthorizationVerdict.NotGranted"/>; the <see cref="AuthorizationVerdict.Denied"/>
+///     variant exists in the model so v2.1 Explicit Deny lands without an API break. Provenance
+///     carries the matched grants (or empty when not granted) for audit + the Admin UI "Probe
+///     this permission" diagnostic.
+/// </summary>
+public sealed record AuthorizationDecision(
+    AuthorizationVerdict Verdict,
+    IReadOnlyList<MatchedGrant> Provenance)
+{
+    public bool IsAllowed => Verdict == AuthorizationVerdict.Allow;
+
+    /// <summary>Convenience constructor for the common "no grants matched" outcome.</summary>
+    public static AuthorizationDecision NotGranted() => new(AuthorizationVerdict.NotGranted, []);
+
+    /// <summary>Allow with the list of grants that matched.</summary>
+    public static AuthorizationDecision Allowed(IReadOnlyList<MatchedGrant> provenance)
+        => new(AuthorizationVerdict.Allow, provenance);
+}
+
+/// <summary>Three-valued authorization outcome.</summary>
+public enum AuthorizationVerdict
+{
+    /// <summary>At least one grant matches the requested (operation, scope) pair.</summary>
+    Allow,
+
+    /// <summary>No grant matches. Phase 6.2 default — treated as deny at the OPC UA surface.</summary>
+    NotGranted,
+
+    /// <summary>Explicit deny grant matched. Reserved for v2.1; never produced by Phase 6.2.</summary>
+    Denied,
+}
+
+/// <summary>One grant that contributed to an Allow verdict — for audit / UI diagnostics.</summary>
+/// <param name="LdapGroup">LDAP group the matched grant belongs to.</param>
+/// <param name="Scope">Where in the hierarchy the grant was anchored.</param>
+/// <param name="PermissionFlags">The bitmask the grant contributed.</param>
+public sealed record MatchedGrant(
+    string LdapGroup,
+    NodeAclScopeKind Scope,
+    NodePermissions PermissionFlags);