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/Server/ZB.MOM.WW.OtOpcUa.Security.Tests/RoleMapperTests.cs

@@ -62,6 +62,7 @@ public sealed class RoleMapperTests
         roles.ShouldBe(new[] { "Administrator" });
     }
 
+    /// <summary>Verifies that Merge unions baseline roles with system-wide DB roles.</summary>
     [Fact]
     public void Merge_unions_baseline_and_systemwide_db_roles()
     {
@@ -76,6 +77,7 @@ public sealed class RoleMapperTests
         result.ShouldNotContain("Designer");   // cluster-scoped row ignored (global-only)
     }
 
+    /// <summary>Verifies that Merge with no DB rows returns the baseline roles unchanged.</summary>
     [Fact]
     public void Merge_with_no_db_rows_returns_baseline()
         => RoleMapper.Merge(["Administrator"], []).ShouldBe(["Administrator"]);