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/Serialization/BundleSerializer.cs

@@ -35,6 +35,7 @@ public sealed class BundleSerializer
     /// build the manifest.
     /// </summary>
     /// <param name="content">The bundle content DTO to serialize.</param>
+    /// <returns>The UTF-8 JSON byte representation of <paramref name="content"/>.</returns>
     public byte[] SerializeContentBytes(BundleContentDto content)
     {
         ArgumentNullException.ThrowIfNull(content);
@@ -48,6 +49,7 @@ public sealed class BundleSerializer
     /// <param name="manifest">The bundle manifest describing the content and encryption metadata.</param>
     /// <param name="passphrase">Passphrase used for encryption; null produces a plaintext bundle.</param>
     /// <param name="encryptor">Encryptor required when <paramref name="passphrase"/> is supplied.</param>
+    /// <returns>A seeked-to-start <see cref="MemoryStream"/> containing the bundle ZIP archive.</returns>
     public Stream Pack(
         BundleContentDto content,
         BundleManifest manifest,
@@ -124,6 +126,7 @@ public sealed class BundleSerializer
     /// Reads and deserializes the manifest entry from a bundle ZIP stream.
     /// </summary>
     /// <param name="zipStream">The ZIP stream containing the bundle.</param>
+    /// <returns>The deserialized <see cref="BundleManifest"/> from the bundle.</returns>
     public BundleManifest ReadManifest(Stream zipStream)
     {
         ArgumentNullException.ThrowIfNull(zipStream);
@@ -145,6 +148,7 @@ public sealed class BundleSerializer
     /// </summary>
     /// <param name="zipStream">The ZIP stream containing the bundle.</param>
     /// <param name="manifest">The bundle manifest used to determine which content entry to read.</param>
+    /// <returns>The raw bytes from the content entry (<c>content.enc</c> or <c>content.json</c>).</returns>
     public byte[] ReadContentBytes(Stream zipStream, BundleManifest manifest)
     {
         ArgumentNullException.ThrowIfNull(zipStream);
@@ -168,6 +172,7 @@ public sealed class BundleSerializer
     /// <param name="manifest">The bundle manifest providing encryption metadata.</param>
     /// <param name="passphrase">Passphrase for decryption; required when the manifest indicates encryption.</param>
     /// <param name="encryptor">Encryptor used for decryption; required when the manifest indicates encryption.</param>
+    /// <returns>The deserialized <see cref="BundleContentDto"/> from the plaintext content.</returns>
     public BundleContentDto UnpackContent(
         byte[] contentBytes,
         BundleManifest manifest,