refactor(adminui): tidy cert-audit review nits (fallthrough comment + single PkiStoreRoot read)

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Certificates/CertificateStoreManager.cs

@@ -29,6 +29,13 @@ public sealed class CertificateStoreManager
     private readonly string _pkiRoot;
     private readonly IAuditWriter _audit;
 
+    /// <summary>
+    /// The resolved PKI store root directory (e.g. <c>pki</c>). Derived once from
+    /// <c>OpcUa:PkiStoreRoot</c> in the production ctor; callers should read this property
+    /// rather than re-resolving the config key independently.
+    /// </summary>
+    public string PkiRoot => _pkiRoot;
+
     /// <summary>Production ctor — reads <c>OpcUa:PkiStoreRoot</c> (default <c>pki</c>).</summary>
     /// <param name="config">App configuration.</param>
     /// <param name="audit">The audit writer that persists Trust/Untrust/Delete actions to <c>ConfigAuditLog</c>.</param>

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Certificates.razor

@@ -127,7 +127,7 @@ else
     private void LoadAll()
     {
         DisposeRows();
-        var pkiRoot = Config.GetValue<string?>("OpcUa:PkiStoreRoot") ?? "pki";
+        var pkiRoot = CertManager.PkiRoot; // Single source: manager already resolved OpcUa:PkiStoreRoot (default "pki").
         _rows = new()
         {
             LoadStore("Own", StoreKind.Own, Path.Combine(pkiRoot, "own", "certs")),
@@ -200,8 +200,14 @@ else
             {
                 StoreKind.Trusted  => CertManager.Delete("trusted", p.Thumbprint, actor),
                 StoreKind.Rejected => CertManager.Delete("rejected", p.Thumbprint, actor),
+                // Unreachable defensive guard — action buttons only render for Trusted/Rejected stores
+                // + the 3 literal verbs (Trust/Untrust/Delete); this arm never executes, so it
+                // intentionally does not route through CertificateStoreManager/audit.
                 _                  => CertActionResult.Fail($"cannot delete from {p.Kind}"),
             },
+            // Unreachable defensive guard — action buttons only render for Trusted/Rejected stores
+            // + the 3 literal verbs (Trust/Untrust/Delete); this arm never executes, so it
+            // intentionally does not route through CertificateStoreManager/audit.
             _ => CertActionResult.Fail("unknown action"),
         };
         _statusError = !result.Success;