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.TemplateEngine/TemplateNaming.cs

@@ -19,6 +19,10 @@ public static class TemplateNaming
     /// stops and falls back to the stored contained name, and a cycle (which
     /// the composition graph should never contain) is broken defensively.
     /// </summary>
+    /// <param name="template">The template whose qualified name to compute.</param>
+    /// <param name="byId">Lookup of all templates by primary key.</param>
+    /// <param name="compById">Lookup of all template compositions by primary key.</param>
+    /// <returns>The dotted hierarchical name (e.g., <c>Owner.Slot.Name</c>).</returns>
     public static string QualifiedName(
         Template template,
         IReadOnlyDictionary<int, Template> byId,