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.AuditLog/Redaction/SafeDefaultAuditRedactor.cs

@@ -37,7 +37,15 @@ public sealed class SafeDefaultAuditRedactor : IAuditRedactor
 
     private SafeDefaultAuditRedactor() { }
 
-    /// <inheritdoc />
+    /// <summary>
+    /// Applies line-oriented header redaction to the default sensitive headers
+    /// (<c>Authorization</c>, <c>X-Api-Key</c>, <c>Cookie</c>, <c>Set-Cookie</c>)
+    /// found in <c>RequestSummary</c> and <c>ResponseSummary</c> inside
+    /// <paramref name="rawEvent"/>.<c>DetailsJson</c>. Never throws; over-redacts on
+    /// any internal failure.
+    /// </summary>
+    /// <param name="rawEvent">The audit event whose details JSON is to be redacted.</param>
+    /// <returns>A new <see cref="AuditEvent"/> with sensitive headers replaced by the redacted marker, or an over-redacted sentinel on failure.</returns>
     public AuditEvent Apply(AuditEvent rawEvent)
     {
         ArgumentNullException.ThrowIfNull(rawEvent);

src/ZB.MOM.WW.ScadaBridge.AuditLog/Redaction/ScadaBridgeAuditRedactor.cs

@@ -73,7 +73,12 @@ public sealed class ScadaBridgeAuditRedactor : IAuditRedactor
         _regexCache = new AuditRegexCache(_logger);
     }
 
-    /// <inheritdoc />
+    /// <summary>
+    /// Applies the full redaction pipeline to <paramref name="rawEvent"/> and returns a
+    /// filtered copy; returns the same instance unchanged on the fast path. Never throws.
+    /// </summary>
+    /// <param name="rawEvent">The raw audit event to redact.</param>
+    /// <returns>A redacted copy of <paramref name="rawEvent"/>, or the original instance when no changes are needed.</returns>
     public AuditEvent Apply(AuditEvent rawEvent)
     {
         try