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.InboundAPI/ParameterValidator.cs

@@ -15,6 +15,7 @@ public static class ParameterValidator
     /// </summary>
     /// <param name="body">The parsed JSON request body; null or undefined if no body was supplied.</param>
     /// <param name="parameterDefinitions">JSON-serialized list of <see cref="ZB.MOM.WW.ScadaBridge.Commons.Types.InboundApi.ParameterDefinition"/>; null or empty means no parameters are defined.</param>
+    /// <returns>A <see cref="ParameterValidationResult"/> with coerced parameter values on success, or an error message on failure.</returns>
     public static ParameterValidationResult Validate(
         JsonElement? body,
         string? parameterDefinitions)
@@ -161,6 +162,7 @@ public class ParameterValidationResult
     /// Creates a successful validation result with the given parameters.
     /// </summary>
     /// <param name="parameters">The validated and coerced parameter values.</param>
+    /// <returns>A <see cref="ParameterValidationResult"/> with <see cref="IsValid"/> set to <c>true</c>.</returns>
     public static ParameterValidationResult Valid(Dictionary<string, object?> parameters) =>
         new() { IsValid = true, Parameters = parameters };
 
@@ -168,6 +170,7 @@ public class ParameterValidationResult
     /// Creates a failed validation result with the given error message.
     /// </summary>
     /// <param name="message">Description of the validation failure.</param>
+    /// <returns>A <see cref="ParameterValidationResult"/> with <see cref="IsValid"/> set to <c>false</c>.</returns>
     public static ParameterValidationResult Invalid(string message) =>
         new() { IsValid = false, ErrorMessage = message };
 }