Phase 1 Stream A — Core.Abstractions project + 11 capability interfaces + DriverTypeRegistry + interface-independence tests

New project src/ZB.MOM.WW.OtOpcUa.Core.Abstractions (.NET 10, BCL-only dependencies, GenerateDocumentationFile=true, TreatWarningsAsErrors=true) defining the contract surface every driver implements. Per docs/v2/plan.md decisions #4 (composable capability interfaces), #52 (streaming IAddressSpaceBuilder), #53 (capability discovery via `is` checks no flag enum), #54 (optional IRediscoverable sub-interface), #59 (Core.Abstractions internal-only for now design as if public).

Eleven capability interfaces:
- IDriver — required lifecycle / health / config-apply / memory-footprint accounting (per driver-stability.md Tier A/B allocation tracking)
- ITagDiscovery — discovers tags streaming to IAddressSpaceBuilder
- IReadable — on-demand reads idempotent for Polly retry
- IWritable — writes NOT auto-retried by default per decisions #44 + #45
- ISubscribable — data-change subscriptions covering both native (Galaxy MXAccess advisory, OPC UA monitored items, TwinCAT ADS) and driver-internal polled (Modbus, AB CIP, S7, FOCAS) mechanisms; OnDataChange callback regardless of source
- IAlarmSource — alarm events + acknowledge + AlarmSeverity enum mirroring acl-design.md NodePermissions alarm-severity values
- IHistoryProvider — HistoryReadRaw + HistoryReadProcessed with continuation points
- IRediscoverable — opt-in change-detection signal; static drivers don't implement
- IHostConnectivityProbe — generalized from Galaxy's GalaxyRuntimeProbeManager per plan §5a
- IDriverConfigEditor — Admin UI plug-point for per-driver custom config editors deferred to each driver's phase per decision #27
- IAddressSpaceBuilder — streaming builder API for driver-driven address-space construction

Plus DTOs: DriverDataType, SecurityClassification (mirroring v1 Galaxy model), DriverAttributeInfo (replaces Galaxy-specific GalaxyAttributeInfo per plan §5a), DriverHealth + DriverState, DataValueSnapshot (universal OPC UA quality + timestamp carrier per decision #13), HostConnectivityStatus + HostState + HostStatusChangedEventArgs, RediscoveryEventArgs, DataChangeEventArgs, AlarmEventArgs + AlarmAcknowledgeRequest + AlarmSeverity, WriteRequest + WriteResult, HistoryReadResult + HistoryAggregateType, ISubscriptionHandle + IAlarmSubscriptionHandle + IVariableHandle.

DriverTypeRegistry singleton with Register / Get / TryGet / All; thread-safe via Interlocked.Exchange snapshot replacement on registration; case-insensitive lookups; rejects duplicate registrations; rejects empty type names. DriverTypeMetadata record carries TypeName + AllowedNamespaceKinds (NamespaceKindCompatibility flags enum per decision #111) + per-config-tier JSON Schemas the validator checks at draft-publish time (decision #91).

Tests project tests/ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests (xUnit v3 1.1.0 matching existing test projects). 24 tests covering: 1) interface independence reflection check (no references outside BCL/System; all public types in root namespace; every capability interface is public); 2) DriverTypeRegistry round-trip, case-insensitive lookups, KeyNotFoundException on unknown, null on TryGet of unknown, InvalidOperationException on duplicate registration (case-insensitive too), All() enumeration, NamespaceKindCompatibility bitmask combinations, ArgumentException on empty type names.

Build: 0 errors, 4 warnings (only pre-existing transitive package vulnerability + analyzer hints). Full test suite: 845 passing / 1 failing — strict improvement over Phase 0 baseline (821/1) by the 24 new Core.Abstractions tests; no regressions in any other test project.

Phase 1 entry-gate record (docs/v2/implementation/entry-gate-phase-1.md) documents the deviation: only Stream A executed in this continuation since Streams B-E need SQL Server / GLAuth / Galaxy infrastructure standup per dev-environment.md Step 1, which is currently TODO.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Core.Abstractions/IAddressSpaceBuilder.cs

@@ -0,0 +1,45 @@
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+/// <summary>
+///     Streaming builder API a driver uses to register OPC UA nodes during discovery.
+///     Core owns the tree; driver streams <c>AddFolder</c> / <c>AddVariable</c> calls
+///     as it discovers nodes — no buffering of the whole tree.
+/// </summary>
+/// <remarks>
+///     Per <c>docs/v2/plan.md</c> decision #52 — drivers register nodes via this builder
+///     rather than returning a tree object. Supports incremental / large address spaces
+///     without forcing the driver to buffer the whole tree.
+/// </remarks>
+public interface IAddressSpaceBuilder
+{
+    /// <summary>
+    ///     Add a folder node. Returns a child builder scoped to inside this folder, so subsequent
+    ///     calls on the child place nodes under it.
+    /// </summary>
+    /// <param name="browseName">OPC UA browse name (the segment of the path under the parent).</param>
+    /// <param name="displayName">Human-readable display name. May equal <paramref name="browseName"/>.</param>
+    IAddressSpaceBuilder Folder(string browseName, string displayName);
+
+    /// <summary>
+    ///     Add a variable node corresponding to a tag. Driver-side full reference + data-type
+    ///     metadata come from the <see cref="DriverAttributeInfo"/> DTO.
+    /// </summary>
+    /// <param name="browseName">OPC UA browse name (the segment of the path under the parent folder).</param>
+    /// <param name="displayName">Human-readable display name. May equal <paramref name="browseName"/>.</param>
+    /// <param name="attributeInfo">Driver-side metadata for the variable.</param>
+    IVariableHandle Variable(string browseName, string displayName, DriverAttributeInfo attributeInfo);
+
+    /// <summary>
+    ///     Add a property to the current node (folder or variable). Properties are static metadata
+    ///     read once at build time (e.g. OPC 40010 Identification fields per the schemas-repo
+    ///     <c>_base</c> equipment-class template).
+    /// </summary>
+    void AddProperty(string browseName, DriverDataType dataType, object? value);
+}
+
+/// <summary>Opaque handle for a registered variable. Used by Core for subscription routing.</summary>
+public interface IVariableHandle
+{
+    /// <summary>Driver-side full reference for read/write addressing.</summary>
+    string FullReference { get; }
+}