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.CLI/Commands/AuditVerifyChainHelpers.cs

@@ -14,6 +14,7 @@ public static class AuditVerifyChainHelpers
     /// with a real month (01-12). A malformed month (e.g. <c>2026-13</c>) is rejected.
     /// </summary>
     /// <param name="month">The month string to validate in YYYY-MM format.</param>
+    /// <returns><c>true</c> if the string is a well-formed YYYY-MM value with a real month; otherwise <c>false</c>.</returns>
     public static bool IsValidMonth(string? month)
         => !string.IsNullOrWhiteSpace(month)
            && DateTime.TryParseExact(month, "yyyy-MM", CultureInfo.InvariantCulture,