docs: complete XML doc comments via fixdocs (2757 to 131 findings)

Add missing <returns>/<param>/<summary>/<typeparam> tags and clean up
misused inheritdoc across 481 files so the documented API surface is
complete. Documentation-only (zero code lines changed). The 131 remaining
findings are inheritdoc-style warnings deliberately left to preserve
hand-written implementation rationale (plan-decision notes, race-condition
explanations).

tests/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/Fakes/FakeSettingsService.cs

@@ -13,15 +13,14 @@ public sealed class FakeSettingsService : ISettingsService
     /// <summary>Gets the last settings that were saved.</summary>
     public UserSettings? LastSaved { get; private set; }
 
-    /// <summary>Loads and returns the current settings.</summary>
+    /// <inheritdoc />
     public UserSettings Load()
     {
         LoadCallCount++;
         return Settings;
     }
 
-    /// <summary>Saves the specified settings.</summary>
-    /// <param name="settings">The settings to save.</param>
+    /// <inheritdoc />
     public void Save(UserSettings settings)
     {
         SaveCallCount++;