docs: add XML doc comments across src + Sister Projects section in CLAUDE.md

Bulk CommentChecker pass: fills in <param>/<inheritdoc> tags on public
APIs across all 23 src/ projects so the doc-coverage gate is green. Also
adds a Sister Projects section to CLAUDE.md pointing at the MxAccess
Gateway and OtOpcUa sibling repos, and gitignores local credential
captures (*login*.txt) and the wonder-app-vd03 deploy/ artifacts.

src/ScadaLink.AuditLog/ServiceCollectionExtensions.cs

@@ -53,6 +53,9 @@ public static class ServiceCollectionExtensions
     /// and the site-→central telemetry collaborators. Idempotent re-registration
     /// is not supported; call this exactly once per <see cref="IServiceCollection"/>.
     /// </summary>
+    /// <param name="services">The service collection to register into.</param>
+    /// <param name="config">Application configuration used to bind <see cref="AuditLogOptions"/> and related options sections.</param>
+    /// <returns>The same <see cref="IServiceCollection"/> for chaining.</returns>
     public static IServiceCollection AddAuditLog(this IServiceCollection services, IConfiguration config)
     {
         ArgumentNullException.ThrowIfNull(services);
@@ -252,6 +255,8 @@ public static class ServiceCollectionExtensions
     /// ships in M6.
     /// </para>
     /// </remarks>
+    /// <param name="services">The service collection to register into.</param>
+    /// <returns>The same <see cref="IServiceCollection"/> for chaining.</returns>
     public static IServiceCollection AddAuditLogHealthMetricsBridge(this IServiceCollection services)
     {
         ArgumentNullException.ThrowIfNull(services);
@@ -290,6 +295,9 @@ public static class ServiceCollectionExtensions
     /// from any composition root" invariant.
     /// </para>
     /// </remarks>
+    /// <param name="services">The service collection to register into.</param>
+    /// <param name="config">Application configuration used to bind partition maintenance options.</param>
+    /// <returns>The same <see cref="IServiceCollection"/> for chaining.</returns>
     public static IServiceCollection AddAuditLogCentralMaintenance(
         this IServiceCollection services,
         IConfiguration config)