fix(sql): Test Connect must construct Postgres and Oracle dialects too

SqlDriverProbe.DefaultDialectFor was left SqlServer-only when the provider
gates were widened, so AdminUI Test Connect failed for both new providers
with InvalidOperationException while Deploy and browse worked. Found by the
live chrome/AdminUI gate the plan deferred, not by any test: every case in
SqlDriverProbeTests builds its probe through ForTest(), which injects the
dialect and never reaches the production switch.

Widen the switch arm-for-arm with SqlDriverFactoryExtensions.CreateDialect,
and cover the gate directly via an internal seam — plus a reserved-provider
falsification control and an end-to-end production-constructor case.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlDriverProbe.cs

@@ -164,11 +164,37 @@ public sealed class SqlDriverProbe : IDriverProbe
         }
     }
 
-    /// <summary>Constructs the production dialect for a provider; v1 supports SQL Server only.</summary>
+    /// <summary>
+    ///     Test seam over <see cref="DefaultDialectFor"/>. The parameterless constructor is the only
+    ///     production path into that switch, and <see cref="ForTest"/> deliberately bypasses it — so without
+    ///     this seam the gate has no direct coverage at all, which is how it kept a SqlServer-only switch
+    ///     after the factory and browser were widened.
+    /// </summary>
+    /// <param name="provider">The provider whose dialect to construct.</param>
+    /// <returns>The dialect this build constructs for <paramref name="provider"/>.</returns>
+    /// <exception cref="InvalidOperationException">The provider is reserved and not constructed.</exception>
+    internal static ISqlDialect DefaultDialectForTest(SqlProvider provider) => DefaultDialectFor(provider);
+
+    /// <summary>
+    ///     Constructs the production dialect for a provider — <b>the same set
+    ///     <see cref="SqlDriverFactoryExtensions"/> constructs</b>, because Test Connect must exercise the
+    ///     backend a Deploy would actually use. This build constructs <see cref="SqlProvider.SqlServer"/>,
+    ///     <see cref="SqlProvider.Postgres"/> and <see cref="SqlProvider.Oracle"/>;
+    ///     <see cref="SqlProvider.MySql"/> and <see cref="SqlProvider.Odbc"/> stay reserved.
+    ///     <para><b>Keep this arm-for-arm with the factory's <c>CreateDialect</c>.</b> When the factory and the
+    ///     browser were widened to Postgres + Oracle this switch was left SqlServer-only, so a config that
+    ///     deployed and browsed fine failed Test Connect with an <see cref="InvalidOperationException"/> — and
+    ///     no test noticed, because every probe test injects its dialect through <see cref="ForTest"/>.</para>
+    /// </summary>
     private static ISqlDialect DefaultDialectFor(SqlProvider provider) => provider switch
     {
         SqlProvider.SqlServer => new SqlServerDialect(),
+        SqlProvider.Postgres => new PostgresDialect(),
+        SqlProvider.Oracle => new OracleDialect(),
         _ => throw new InvalidOperationException(
-            $"provider '{provider}' is not available in this build (only SqlServer is supported)."),
+            $"provider '{provider}' is not available in this build. Supported: " +
+            $"'{nameof(SqlProvider.SqlServer)}', '{nameof(SqlProvider.Postgres)}', " +
+            $"'{nameof(SqlProvider.Oracle)}'. Reserved (declared on the enum but not implemented): " +
+            $"'{nameof(SqlProvider.MySql)}', '{nameof(SqlProvider.Odbc)}'."),
     };
 }