chore: organize solution into module folders (Core/Server/Drivers/Client/Tooling)

Group all 69 projects into category subfolders under src/ and tests/ so the
Rider Solution Explorer mirrors the module structure. Folders: Core, Server,
Drivers (with a nested Driver CLIs subfolder), Client, Tooling.

- Move every project folder on disk with git mv (history preserved as renames).
- Recompute relative paths in 57 .csproj files: cross-category ProjectReferences,
  the lib/ HintPath+None refs in Driver.Historian.Wonderware, and the external
  mxaccessgw refs in Driver.Galaxy and its test project.
- Rebuild ZB.MOM.WW.OtOpcUa.slnx with nested solution folders.
- Re-prefix project paths in functional scripts (e2e, compliance, smoke SQL,
  integration, install).

Build green (0 errors); unit tests pass. Docs left for a separate pass.

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

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

@@ -0,0 +1,60 @@
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+/// <summary>
+///     Required capability for every driver instance. Owns lifecycle, metadata, health.
+///     Other capabilities (<see cref="ITagDiscovery"/>, <see cref="IReadable"/>,
+///     <see cref="IWritable"/>, <see cref="ISubscribable"/>, <see cref="IAlarmSource"/>,
+///     <see cref="IHistoryProvider"/>, <see cref="IRediscoverable"/>,
+///     <see cref="IHostConnectivityProbe"/>) are composable — a driver implements only what its
+///     backend actually supports.
+/// </summary>
+/// <remarks>
+///     Per <c>docs/v2/plan.md</c> decisions #4 (composable capability interfaces) and #53
+///     (capability discovery via <c>is</c> checks — no redundant flag enum).
+/// </remarks>
+public interface IDriver
+{
+    /// <summary>Stable logical ID of this driver instance, sourced from the central config DB.</summary>
+    string DriverInstanceId { get; }
+
+    /// <summary>Driver type name (e.g. "Galaxy", "ModbusTcp", "AbCip"). Matches <c>DriverInstance.DriverType</c>.</summary>
+    string DriverType { get; }
+
+    /// <summary>Initialize the driver from its <c>DriverConfig</c> JSON; open connections; prepare for first use.</summary>
+    Task InitializeAsync(string driverConfigJson, CancellationToken cancellationToken);
+
+    /// <summary>
+    ///     Apply a config change in place without tearing down the driver process.
+    ///     Used by <c>IGenerationApplier</c> when only this driver's config changed in the new generation.
+    /// </summary>
+    /// <remarks>
+    ///     Per <c>docs/v2/driver-stability.md</c> §"In-process only (Tier A/B)" — Reinitialize is the
+    ///     only Core-initiated recovery path for in-process drivers; if it fails, the driver instance
+    ///     is marked Faulted and its nodes go Bad quality, but the server process keeps running.
+    /// </remarks>
+    Task ReinitializeAsync(string driverConfigJson, CancellationToken cancellationToken);
+
+    /// <summary>Stop the driver, close connections, release resources. Called on shutdown or driver removal.</summary>
+    Task ShutdownAsync(CancellationToken cancellationToken);
+
+    /// <summary>Current health snapshot, polled by Core for the status dashboard and ServiceLevel.</summary>
+    DriverHealth GetHealth();
+
+    /// <summary>
+    ///     Approximate driver-attributable footprint in bytes (caches, queues, symbol tables).
+    ///     Polled every 30s by Core; on cache-budget breach, Core asks the driver to flush via
+    ///     <see cref="FlushOptionalCachesAsync"/>.
+    /// </summary>
+    /// <remarks>
+    ///     Per <c>docs/v2/driver-stability.md</c> §"In-process only (Tier A/B) — driver-instance
+    ///     allocation tracking". Tier C drivers (process-isolated) report through the same
+    ///     interface but the cache-flush is internal to their host.
+    /// </remarks>
+    long GetMemoryFootprint();
+
+    /// <summary>
+    ///     Drop optional caches (symbol cache, browse cache, etc.) to bring footprint back below budget.
+    ///     Required-for-correctness state must NOT be flushed.
+    /// </summary>
+    Task FlushOptionalCachesAsync(CancellationToken cancellationToken);
+}