fix(historian): map Boolean historization to Int2, not degenerate Int1 (#441)

The historian's Int1 analog-tag creation path is server-degenerate:
EnsureTags(Int1) stores an unusable stub (live-probed on the deployed
2023 R2 historian; root-caused + documented gateway-side in
HistorianGateway #11 / PR #16). HistorianTypeMapper mapped
DriverDataType.Boolean -> HistorianDataType.Int1, so Boolean historized
tags failed auto-provisioning.

Map Boolean -> Int2 instead (store 0/1). Int2 is a proven-creatable
analog type, and the value-write path already sends every value as a
double on WriteLiveValues regardless of tag type, so Boolean 0.0/1.0
round-trips cleanly. Both Float and Int2 are supported, so a
pre-existing Float Boolean tag retypes cleanly on its next deploy.

- HistorianTypeMapper: Boolean => Int2 (+ remarks)
- Unit pins: HistorianTypeMapperTests, GatewayTagProvisionerTests
  (Boolean_definition_carries_explicit_Int2_presence)
- Live gate: EnsureTags_boolean_sandbox_provisions_as_Int2 (was _Int1);
  retype probe reframed Float->Int2 (drops the dead Int1 leg)
- Docs: docs/Historian.md 'Boolean historization maps to Int2', CLAUDE.md,
  archreview STATUS.md (R2-06 live gate -> 6/6)

Resolves #441.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/HistorianTypeMapper.cs

@@ -9,11 +9,14 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Mapping;
 /// </summary>
 /// <remarks>
 /// Only the nine numeric types are historizable on the gateway's analog write path. Two of them
-/// fall back to a wider historian type because the narrower one's write path is deferred upstream:
-/// <see cref="DriverDataType.UInt16"/> maps to <see cref="HistorianDataType.Uint4"/> (the historian's
-/// <c>UInt2</c> write path is not proven). String / DateTime / Reference are not historized in v1
-/// and throw <see cref="NotSupportedException"/>; callers that want to skip them without catching an
-/// exception should consult <see cref="IsHistorizable(DriverDataType)"/> first.
+/// fall back to a wider/adjacent historian type because the exact one's write path is not usable
+/// upstream: <see cref="DriverDataType.UInt16"/> maps to <see cref="HistorianDataType.Uint4"/> (the
+/// historian's <c>UInt2</c> write path is not proven), and <see cref="DriverDataType.Boolean"/> maps
+/// to <see cref="HistorianDataType.Int2"/> — the historian's <c>Int1</c> analog-tag creation path is
+/// server-degenerate (issue #441 / HistorianGateway #11: <c>EnsureTags(Int1)</c> stores an unusable
+/// stub), so Boolean historizes as a small 0/1 integer instead. String / DateTime / Reference are not
+/// historized in v1 and throw <see cref="NotSupportedException"/>; callers that want to skip them
+/// without catching an exception should consult <see cref="IsHistorizable(DriverDataType)"/> first.
 /// </remarks>
 internal static class HistorianTypeMapper
 {
@@ -25,7 +28,8 @@ internal static class HistorianTypeMapper
     /// </exception>
     public static HistorianDataType ToHistorianDataType(DriverDataType dataType) => dataType switch
     {
-        DriverDataType.Boolean => HistorianDataType.Int1,
+        DriverDataType.Boolean => HistorianDataType.Int2, // Int1 analog-tag creation is server-degenerate (issue #441) → store 0/1
+
         DriverDataType.Int16 => HistorianDataType.Int2,
         DriverDataType.Int32 => HistorianDataType.Int4,
         DriverDataType.Int64 => HistorianDataType.Int8,