docs: complete XML doc coverage (returns, summaries, inheritdoc)

Resolve all 622 issues flagged by the enhanced CommentChecker: add missing
<returns> tags (incl. the standard phrasing on non-generic Task methods),
add missing <summary> tags, and replace misused/redundant <inheritdoc/> on
members that override or implement nothing with real documentation.
Documentation-only — no behavior change; solution builds clean.

src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/SandboxScriptHost.cs

@@ -102,6 +102,7 @@ public interface ISandboxInstanceGateway
     /// <param name="canonicalName">The canonical name of the attribute.</param>
     /// <param name="value">The value to set.</param>
     /// <param name="ct">Cancellation token.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     Task SetAttributeAsync(string canonicalName, string value, CancellationToken ct);
 
     /// <summary>