feat(acl): keys + ACLs reach driver-only nodes via the artifact (#520 stage 4)

A driver-only node has had no ConfigDb since per-cluster mesh Phase 4, so it
registered NullOpcUaUserAuthenticator and denied every UserName token. Its keys
now ride the deployment artifact instead.

- ConfigComposer snapshots ApiKeys alongside the NodeAcls it already carried.
  Only the peppered HMAC ships, never a secret, and the pepper is node config
  that is deliberately not in the artifact.
- DeploymentArtifact.ParseDataPlaneAuthority decodes both node-side. Grants are
  scoped to the node's own cluster; keys are not, because ApiKey carries no
  ClusterId — a key is a fleet-wide credential and the ACL rows are what bind it.
- OpcUaPublishActor installs them on DataPlaneAuthorityState on every apply,
  BEFORE its plan.IsEmpty early-return: an artifact that only revokes a key
  produces an empty address-space plan, so feeding after that return would leave
  the revoked key working until an unrelated structural change redeployed.
- ArtifactApiKeyStore serves them to session activation; a node with a ConfigDb
  keeps ConfigDbApiKeyStore, whose per-request read is what makes revocation
  immediate there.
- OtOpcUaNodeManager gains DataPlaneAuthority — the cluster identity blocker #4
  named. NodeScope.ClusterId is required and the evaluator fails closed on a
  mismatch, so until now no scope it built could have evaluated. Nothing reads it
  until stages 5/6.

The generation is a node-local COUNTER driven by the RevisionHash, not derived
from its bits. PermissionTrieCache treats the highest GenerationId as current, so
a generation taken from hash bytes would install a lower number about half the
time and the cache would go on serving the previous deployment's ACLs, silently.

Sessions are not stamped with it yet — that belongs with the first seam that
reads a UserAuthorizationState, in stage 5, rather than being built now and
consulted by nothing.

Live-gated on docker-dev against site-a-1 (driver-only, no ConfigDb): key
authenticates, wrong secret denied, both halves of the revocation asymmetry
observed, and a SITE-A grant confirmed not to reach site-b-1. Key minted with an
independent Python HMAC so the verifier was checked against something other than
itself. Rig left clean.

Claude-Session: https://claude.ai/code/session_015p7wGqy3YpZNCpDzTpGMKo

src/Server/ZB.MOM.WW.OtOpcUa.Host/OpcUa/ArtifactApiKeyStore.cs

@@ -0,0 +1,80 @@
+using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
+// Fully-qualified rather than relative: this file's own namespace root contains a `Configuration`
+// namespace (ZB.MOM.WW.OtOpcUa.Host.Configuration), so a relative `Configuration.Enums` binds there and
+// fails to compile.
+using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
+using ZB.MOM.WW.OtOpcUa.Core.Authorization;
+
+namespace ZB.MOM.WW.OtOpcUa.Host.OpcUa;
+
+/// <summary>
+///     <see cref="IApiKeyStore"/> served from the deployment artifact (#520, stage 4). This is the key
+///     source for a <b>driver-only</b> node, which has had no ConfigDb since per-cluster mesh Phase 4 and
+///     until now denied every UserName token.
+/// </summary>
+/// <remarks>
+///     <para>
+///         Purely in-memory: <see cref="OpcUaPublishActor"/> decodes the keys and grants once per applied
+///         artifact and installs them on <see cref="IDataPlaneAuthoritySource"/>. That matters because the
+///         SDK raises the impersonation callback <b>synchronously, under a <c>SessionManager</c>-wide
+///         lock</b> — an I/O-bound lookup here would serialize every session activation in the server
+///         behind one disk or network round trip.
+///     </para>
+///     <para>
+///         ⚠️ <b>Consequence: revocation lands on the next deployment, not immediately.</b> A node reading
+///         the ConfigDb sees <c>Enabled = 0</c> on the next request; this one sees it only once a new
+///         artifact arrives. That asymmetry is inherent to a node with no config database and is
+///         documented for operators on the AdminUI key page.
+///     </para>
+///     <para>
+///         Before the first artifact is applied the snapshot is empty, so every key is denied. That is the
+///         safe direction, and it is also honest — a node that has not been deployed to has no configured
+///         keys.
+///     </para>
+/// </remarks>
+public sealed class ArtifactApiKeyStore : IApiKeyStore
+{
+    private readonly IDataPlaneAuthoritySource _authority;
+
+    /// <summary>Initializes a new instance of the <see cref="ArtifactApiKeyStore"/> class.</summary>
+    /// <param name="authority">The node's current data-plane authorization inputs.</param>
+    public ArtifactApiKeyStore(IDataPlaneAuthoritySource authority)
+    {
+        ArgumentNullException.ThrowIfNull(authority);
+        _authority = authority;
+    }
+
+    /// <inheritdoc />
+    public Task<ApiKeyLookup?> FindAsync(string apiKeyId, DateTime utcNow, CancellationToken ct)
+    {
+        // Read the snapshot ONCE. Re-reading Current for the grants would let a deploy land between the
+        // two reads and pair a key from one generation with grants from another.
+        var snapshot = _authority.Current;
+        var key = snapshot.FindUsableKey(apiKeyId, utcNow);
+        return Task.FromResult(key is null
+            ? null
+            : new ApiKeyLookup(key, ClusterGrants(snapshot, key.Principal)));
+    }
+
+    /// <inheritdoc />
+    public Task<IReadOnlyList<NodeAcl>> FindGrantsAsync(string principal, CancellationToken ct) =>
+        Task.FromResult(ClusterGrants(_authority.Current, principal));
+
+    /// <summary>
+    ///     Narrows a principal's grants to the Cluster-scoped ones, matching <c>ConfigDbApiKeyStore</c>.
+    ///     Only those confer an interim role (see <see cref="ApiKeyInterimRoleMapper"/>); stage 5 widens
+    ///     both stores to the full grant set once scope is actually enforced.
+    /// </summary>
+    private static IReadOnlyList<NodeAcl> ClusterGrants(DataPlaneAuthoritySnapshot snapshot, string principal)
+    {
+        var all = snapshot.GrantsFor(principal);
+        if (all.Count == 0) return [];
+
+        var scoped = new List<NodeAcl>(all.Count);
+        foreach (var grant in all)
+        {
+            if (grant.ScopeKind == NodeAclScopeKind.Cluster) scoped.Add(grant);
+        }
+        return scoped;
+    }
+}