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.StoreAndForward/StoreAndForwardStorage.cs

@@ -41,6 +41,7 @@ public class StoreAndForwardStorage
     /// <summary>
     /// Creates the sf_messages table if it does not exist.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task InitializeAsync()
     {
         EnsureDatabaseDirectoryExists();
@@ -145,6 +146,7 @@ public class StoreAndForwardStorage
     /// WP-9: Enqueues a new message with Pending status.
     /// </summary>
     /// <param name="message">The message to enqueue.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task EnqueueAsync(StoreAndForwardMessage message)
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -190,6 +192,7 @@ public class StoreAndForwardStorage
     /// <summary>
     /// WP-10: Gets all messages that are due for retry (Pending status, last attempt older than retry interval).
     /// </summary>
+    /// <returns>A task that resolves to the list of messages due for retry, ordered by creation time ascending.</returns>
     public async Task<List<StoreAndForwardMessage>> GetMessagesForRetryAsync()
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -216,6 +219,7 @@ public class StoreAndForwardStorage
     /// WP-10: Updates a message after a delivery attempt.
     /// </summary>
     /// <param name="message">The message with updated retry count, status, and last error.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task UpdateMessageAsync(StoreAndForwardMessage message)
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -255,6 +259,7 @@ public class StoreAndForwardStorage
     /// </summary>
     /// <param name="message">The message with the updated values to persist.</param>
     /// <param name="expectedStatus">The status the row must currently have for the update to proceed.</param>
+    /// <returns>A task that resolves to <c>true</c> if the row was updated; <c>false</c> if its status had already changed.</returns>
     public async Task<bool> UpdateMessageIfStatusAsync(
         StoreAndForwardMessage message,
         StoreAndForwardMessageStatus expectedStatus)
@@ -287,6 +292,7 @@ public class StoreAndForwardStorage
     /// WP-10: Removes a successfully delivered message.
     /// </summary>
     /// <param name="messageId">The id of the message to remove.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task RemoveMessageAsync(string messageId)
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -311,6 +317,7 @@ public class StoreAndForwardStorage
     /// <param name="category">Optional category filter; null returns parked messages from all categories.</param>
     /// <param name="pageNumber">1-based page number.</param>
     /// <param name="pageSize">Maximum number of messages to return per page.</param>
+    /// <returns>A task that resolves to the page of parked messages and the total count of matching rows.</returns>
     public async Task<(List<StoreAndForwardMessage> Messages, int TotalCount)> GetParkedMessagesAsync(
         StoreAndForwardCategory? category = null,
         int pageNumber = 1,
@@ -366,6 +373,7 @@ public class StoreAndForwardStorage
     /// by accident, and a long interval would instead delay the operator's retry.
     /// </summary>
     /// <param name="messageId">The id of the parked message to move back to Pending.</param>
+    /// <returns>A task that resolves to <c>true</c> if the message was found and reset to Pending; <c>false</c> if not found or not in Parked status.</returns>
     public async Task<bool> RetryParkedMessageAsync(string messageId)
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -389,6 +397,7 @@ public class StoreAndForwardStorage
     /// WP-12: Permanently discards a parked message.
     /// </summary>
     /// <param name="messageId">The id of the parked message to discard.</param>
+    /// <returns>A task that resolves to <c>true</c> if the message was found and deleted; <c>false</c> if not found or not in Parked status.</returns>
     public async Task<bool> DiscardParkedMessageAsync(string messageId)
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -406,6 +415,7 @@ public class StoreAndForwardStorage
     /// <summary>
     /// WP-14: Gets buffer depth by category (count of pending messages per category).
     /// </summary>
+    /// <returns>A task that resolves to a dictionary mapping each category to its pending message count.</returns>
     public async Task<Dictionary<StoreAndForwardCategory, int>> GetBufferDepthByCategoryAsync()
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -436,6 +446,7 @@ public class StoreAndForwardStorage
     /// Returns the count of messages for a given origin instance.
     /// </summary>
     /// <param name="instanceName">The origin instance name to count messages for.</param>
+    /// <returns>A task that resolves to the number of messages whose origin instance matches <paramref name="instanceName"/>.</returns>
     public async Task<int> GetMessageCountByOriginInstanceAsync(string instanceName)
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -455,6 +466,7 @@ public class StoreAndForwardStorage
     /// Gets a message by ID.
     /// </summary>
     /// <param name="messageId">The id of the message to retrieve.</param>
+    /// <returns>A task that resolves to the matching message, or <c>null</c> if not found.</returns>
     public async Task<StoreAndForwardMessage?> GetMessageByIdAsync(string messageId)
     {
         await using var connection = new SqliteConnection(_connectionString);
@@ -476,6 +488,7 @@ public class StoreAndForwardStorage
     /// <summary>
     /// Gets the count of parked messages (for health reporting).
     /// </summary>
+    /// <returns>A task that resolves to the number of messages currently in Parked status.</returns>
     public async Task<int> GetParkedMessageCountAsync()
     {
         await using var conn = new SqliteConnection(_connectionString);
@@ -491,6 +504,7 @@ public class StoreAndForwardStorage
     /// Gets total message count by status.
     /// </summary>
     /// <param name="status">The status to filter by.</param>
+    /// <returns>A task that resolves to the count of messages with the specified status.</returns>
     public async Task<int> GetMessageCountByStatusAsync(StoreAndForwardMessageStatus status)
     {
         await using var connection = new SqliteConnection(_connectionString);