Resolve IntegrationTests-025: stopBoundary for repo-root walker

ResolveRepositoryRoot accepts an optional stopBoundary parameter that
caps the upward walk; production callers pass null and behavior is
unchanged. The two repository-marker tests now seal their walkers
inside their own temp directories, so a redirected TMP or a co-located
C:\src checkout no longer leaks ambient marker-bearing ancestors into
the assertion.

Regression test ResolveRepositoryRoot_StopBoundary_IsolatesWalkerFromAmbientAncestorMarkers
constructs an outer ancestor that carries src/ + .git, confirms the
walker leaks into it without the boundary, then asserts the same call
throws with the boundary supplied.

Resolved at 2026-05-24; IntegrationTestEnvironmentTests 5/5 pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.MxGateway.IntegrationTests/IntegrationTestEnvironment.cs

@@ -109,12 +109,26 @@ public static class IntegrationTestEnvironment
     /// remains the escape hatch for unusual deployments.
     /// </summary>
     /// <param name="startDirectory">Starting directory to search from.</param>
+    /// <param name="stopBoundary">
+    /// Optional upper bound for the parent walk. When supplied, the walker checks
+    /// <paramref name="stopBoundary"/> for markers and then stops, ignoring all
+    /// ancestors above it. Tests pass an isolated boundary so the walker cannot
+    /// leak into ambient ancestors (a redirected <c>TMP</c>, a co-located checkout
+    /// at <c>C:\src</c>, an enclosing CI workspace, etc.) that would silently
+    /// satisfy <see cref="IsRepositoryRoot"/> — see IntegrationTests-025.
+    /// Production callers pass <see langword="null"/> so the walk continues to the
+    /// drive root as before.
+    /// </param>
     /// <returns>The repository root path.</returns>
     /// <exception cref="InvalidOperationException">
     /// Thrown when the parent walk exhausts without finding a repository root.
     /// </exception>
-    internal static string ResolveRepositoryRoot(string startDirectory)
+    internal static string ResolveRepositoryRoot(string startDirectory, string? stopBoundary = null)
     {
+        string? normalizedBoundary = stopBoundary is null
+            ? null
+            : Path.TrimEndingDirectorySeparator(Path.GetFullPath(stopBoundary));
+
         DirectoryInfo? directory = new(startDirectory);
         while (directory is not null)
         {
@@ -123,6 +137,15 @@ public static class IntegrationTestEnvironment
                 return directory.FullName;
             }
 
+            if (normalizedBoundary is not null
+                && string.Equals(
+                    Path.TrimEndingDirectorySeparator(directory.FullName),
+                    normalizedBoundary,
+                    StringComparison.OrdinalIgnoreCase))
+            {
+                break;
+            }
+
             directory = directory.Parent;
         }