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.Transport/Import/BundleUnlockRateLimiter.cs

@@ -122,6 +122,8 @@ public sealed class BundleUnlockRateLimiter
     /// within the trailing window. Primarily for tests / diagnostics; not part of the
     /// hot-path.
     /// </summary>
+    /// <param name="clientKey">Opaque caller identifier — typically the remote IP.</param>
+    /// <returns>The number of recorded attempts for the key that still fall within the trailing window.</returns>
     public int GetAttemptCount(string clientKey)
     {
         ArgumentException.ThrowIfNullOrWhiteSpace(clientKey);
@@ -150,6 +152,7 @@ public sealed class BundleUnlockRateLimiter
     /// </summary>
     private sealed class AttemptBucket
     {
+        /// <summary>Ordered queue of attempt timestamps within the current trailing window.</summary>
         public Queue<DateTimeOffset> Timestamps { get; } = new();
     }
 }