fix(sql): withhold the JSON parser's text on a malformed driver config (R06:S-8)

The factory quoted System.Text.Json's message (and attached the JsonException) into
the failure that reaches InitializeFailed -> health LastError -> /hosts; a pasted
connection-string literal is exactly the malformed text that lands there. The
message now names the instance and the line/byte position only, as the probe and
browser already do.

Refs #744
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlDriverFactoryExtensions.cs

@@ -194,8 +194,14 @@ public static class SqlDriverFactoryExtensions
         }
         catch (JsonException ex)
         {
+            // The parser's message AND the exception carrying it are withheld (R06:S-8), matching
+            // SqlDriverProbe and SqlDriverBrowser: System.Text.Json quotes the offending token, and a pasted
+            // connection-string literal is exactly the malformed text that lands here. This message becomes
+            // InitializeFailed -> health LastError -> /hosts. Line/byte position carry no content, so they stay.
             throw new InvalidOperationException(
-                $"Sql driver config for '{driverInstanceId}' is not valid JSON: {ex.Message}", ex);
+                $"Sql driver config for '{driverInstanceId}' is not valid JSON (line {ex.LineNumber + 1}, byte "
+                + $"{ex.BytePositionInLine}). The parser's message is withheld because the malformed text may "
+                + "carry a connection string.");
         }
     }
 

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Tests/SqlDriverFactoryTests.cs

@@ -25,6 +25,28 @@ public sealed class SqlDriverFactoryTests
 {
     // ---- the plan's headline legs ----
 
+    /// <summary>
+    ///     <b>R06:S-8.</b> A malformed config used to quote System.Text.Json's message — which echoes the
+    ///     offending token — into the exception that becomes <c>InitializeFailed</c> → health
+    ///     <c>LastError</c> → <c>/hosts</c>. A pasted connection string is exactly the malformed text that
+    ///     reaches here, so the parser text (and the inner exception carrying it) is withheld, as the probe and
+    ///     browser already do. The message still names the instance and says what is wrong.
+    /// </summary>
+    [Fact]
+    public void CreateInstance_malformedJson_withholdsTheParserText()
+    {
+        const string secret = "hunter2-do-not-log";
+        var ex = Should.Throw<InvalidOperationException>(() =>
+            SqlDriverFactoryExtensions.CreateInstance(
+                "d1", $$"""{"provider":"SqlServer","connectionStringRef": Password={{secret}} }""", null));
+
+        ex.Message.ShouldContain("d1");
+        ex.Message.ShouldContain("not valid JSON");
+        ex.Message.ShouldNotContain(secret);
+        ex.Message.ShouldNotContain("Password");
+        ex.InnerException.ShouldBeNull();
+    }
+
     [Fact]
     public void CreateInstance_missingConnectionStringRef_throwsActionable()
         => Should.Throw<InvalidOperationException>(() =>