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/Payload/AuditRedactionPrimitives.cs

@@ -71,6 +71,11 @@ internal static class AuditRedactionPrimitives
     /// field is over-redacted with <see cref="RedactorErrorMarker"/> and
     /// <paramref name="onFailure"/> is invoked.
     /// </summary>
+    /// <param name="json">The raw JSON string to redact; null passes through as null.</param>
+    /// <param name="redactList">Header names (case-insensitive) whose values should be replaced.</param>
+    /// <param name="logger">Logger for warning diagnostics on redactor faults.</param>
+    /// <param name="onFailure">Callback invoked when the redactor stage faults; used to increment health counters.</param>
+    /// <returns>The re-serialized JSON with redacted header values, the original string if nothing was redacted, or <see cref="RedactorErrorMarker"/> on fault.</returns>
     public static string? RedactHeaders(
         string? json,
         IList<string> redactList,
@@ -152,6 +157,11 @@ internal static class AuditRedactionPrimitives
     /// with <see cref="RedactorErrorMarker"/> and <paramref name="onFailure"/>
     /// is invoked — the user-facing action is never aborted.
     /// </summary>
+    /// <param name="value">The string to redact; null passes through as null.</param>
+    /// <param name="regexes">Compiled body-redaction regexes applied in order.</param>
+    /// <param name="logger">Logger for warning diagnostics on redactor faults.</param>
+    /// <param name="onFailure">Callback invoked when a regex match faults; used to increment health counters.</param>
+    /// <returns>The value with all regex matches replaced by <see cref="RedactedMarker"/>, or <see cref="RedactorErrorMarker"/> on fault.</returns>
     public static string? RedactBody(
         string? value,
         IReadOnlyList<Regex> regexes,
@@ -192,6 +202,11 @@ internal static class AuditRedactionPrimitives
     /// is over-redacted with <see cref="RedactorErrorMarker"/> and
     /// <paramref name="onFailure"/> is invoked.
     /// </summary>
+    /// <param name="json">The raw JSON string to redact; null passes through as null.</param>
+    /// <param name="paramNameRegex">Compiled regex matched against each SQL parameter name.</param>
+    /// <param name="logger">Logger for warning diagnostics on redactor faults.</param>
+    /// <param name="onFailure">Callback invoked when the redactor stage faults; used to increment health counters.</param>
+    /// <returns>The re-serialized JSON with matched parameter values replaced by <see cref="RedactedMarker"/>, the original string if no parameters matched, or <see cref="RedactorErrorMarker"/> on fault.</returns>
     public static string? RedactSqlParameters(
         string? json,
         Regex paramNameRegex,
@@ -277,6 +292,10 @@ internal static class AuditRedactionPrimitives
     /// setting <paramref name="truncated"/> to <c>true</c> when the value was
     /// shortened. Null passes through as null.
     /// </summary>
+    /// <param name="value">The string to truncate; null passes through as null.</param>
+    /// <param name="cap">Maximum number of UTF-8 bytes to retain.</param>
+    /// <param name="truncated">Set to <c>true</c> when the value was shortened; unchanged otherwise.</param>
+    /// <returns>The truncated string, the original string if within the cap, or <c>null</c> if the input was null.</returns>
     public static string? TruncateField(string? value, int cap, ref bool truncated)
     {
         if (value is null)
@@ -299,6 +318,9 @@ internal static class AuditRedactionPrimitives
     /// (<c>byte &amp; 0xC0 == 0x80</c>), and decodes the resulting prefix —
     /// guaranteeing the returned string never splits a multi-byte sequence.
     /// </summary>
+    /// <param name="value">The string to truncate.</param>
+    /// <param name="capBytes">Maximum number of UTF-8 bytes in the returned string.</param>
+    /// <returns>The truncated string guaranteed not to split a multi-byte UTF-8 sequence, or the original string if within the cap.</returns>
     public static string TruncateUtf8(string value, int capBytes)
     {
         if (string.IsNullOrEmpty(value))

src/ZB.MOM.WW.ScadaBridge.AuditLog/Payload/AuditRegexCache.cs

@@ -35,6 +35,8 @@ internal sealed class AuditRegexCache
     private readonly ConcurrentDictionary<string, CompiledRegex> _cache = new();
     private readonly ILogger _logger;
 
+    /// <summary>Initializes the cache with the logger used to report compile failures.</summary>
+    /// <param name="logger">Logger for recording invalid or slow-compile pattern warnings.</param>
     public AuditRegexCache(ILogger logger) => _logger = logger;
 
     /// <summary>
@@ -44,6 +46,9 @@ internal sealed class AuditRegexCache
     /// compile time "invalid"); the failure is logged once and the sentinel
     /// cache entry prevents repeat compile attempts.
     /// </summary>
+    /// <param name="pattern">The regex pattern string to look up or compile.</param>
+    /// <param name="regex">The compiled <see cref="Regex"/>, or <c>null</c> if the pattern is invalid.</param>
+    /// <returns><c>true</c> if the pattern compiled successfully; <c>false</c> if it is invalid or too slow to compile.</returns>
     public bool TryGet(string pattern, out Regex? regex)
     {
         var entry = _cache.GetOrAdd(pattern, Compile);
@@ -88,8 +93,11 @@ internal sealed class AuditRegexCache
     {
         public static readonly CompiledRegex Invalid = new(null);
 
+        /// <summary>The compiled regex, or <c>null</c> when this entry represents an invalid pattern.</summary>
         public Regex? Regex { get; }
 
+        /// <summary>Initializes the entry with the compiled regex (or <c>null</c> for the invalid sentinel).</summary>
+        /// <param name="regex">The compiled <see cref="Regex"/>, or <c>null</c> for a failed compile.</param>
         public CompiledRegex(Regex? regex) => Regex = regex;
     }
 }