feat(sql): register Sql factory + probe in Host, add DriverTypeNames.Sql

Add DriverTypeNames.Sql (+ All) as the shared source of truth, and wire the driver
into the Host: register the factory in DriverFactoryBootstrap.Register via
Driver.Sql.SqlDriverFactoryExtensions.Register(registry, loggerFactory), add the
SqlProbe (= Driver.Sql.SqlDriverProbe) probe via TryAddEnumerable, and add the
Driver.Sql project reference to the Host. Default tier A (SQL client is managed +
cross-platform, so ShouldStub needs no change).

Repoint the interim SqlDriver.DriverTypeName / SqlDriverFactoryExtensions.DriverTypeName
literals at DriverTypeNames.Sql; both still resolve to "Sql", so the AdminUI
TagConfigEditorMap/TagConfigValidator keys and the DriverTypeName-parity test stay
green. The Core guard test discovers factories from its own bin, so it also gains a
Driver.Sql project reference — that is the "registered-factory side" that lets
DriverTypeNamesGuardTests' bidirectional-parity check pass (4/4 green).

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

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

@@ -29,14 +29,12 @@ public sealed class SqlDriver
     : IDriver, ITagDiscovery, IReadable, ISubscribable, IHostConnectivityProbe, IAsyncDisposable
 {
     /// <summary>
-    ///     The driver-type string this driver registers under.
-    ///     <para><b>Deliberately a local constant, not <c>DriverTypeNames.Sql</c>.</b>
-    ///     <c>DriverTypeNamesGuardTests</c> asserts bidirectional parity between the constants and the
-    ///     driver factories actually registered in the process, so the constant may only be added in the
-    ///     same change that wires the factory (this task ships no factory — see the plan's Task 11, which
-    ///     adds <c>DriverTypeNames.Sql</c> and repoints this constant at it).</para>
+    ///     The driver-type string this driver registers under — <see cref="DriverTypeNames.Sql"/>, the single
+    ///     source of truth the deploy pipeline stores in <c>DriverInstance.DriverType</c> and every dispatch
+    ///     map keys by. Chained off the shared constant (Task 11 wired the factory + probe, so
+    ///     <c>DriverTypeNamesGuardTests</c>' bidirectional-parity check is satisfied).
     /// </summary>
-    public const string DriverTypeName = "Sql";
+    public const string DriverTypeName = DriverTypeNames.Sql;
 
     /// <summary>Shown for a connection string that names no recognisable server.</summary>
     private const string UnknownEndpoint = "(unknown sql endpoint)";