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.SiteRuntime/Scripts/TriggerExpressionGlobals.cs

@@ -20,6 +20,7 @@ public sealed class TriggerExpressionGlobals
     /// and AlarmActor.
     /// </summary>
     /// <param name="triggerConfigJson">JSON string of the trigger configuration, or null.</param>
+    /// <returns>The expression string, or <c>null</c> if the config is missing, blank, or malformed.</returns>
     public static string? ExtractExpression(string? triggerConfigJson)
     {
         if (string.IsNullOrEmpty(triggerConfigJson)) return null;