fix: update integration tests to use Reader() method instead of reader field

PR #238 removed the `reader` field from the Executor struct and replaced
it with a Reader() method. Two integration test files still referenced
the old field, breaking the CI integration test build.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ako

mdl/executor/roundtrip_doctype_test.go

@@ -137,7 +137,7 @@ func TestMxCheck_DoctypeScripts(t *testing.T) {
 			}
 
 			// Filter out version-gated sections that don't match this project's Mendix version
-			pv := env.executor.reader.ProjectVersion()
+			pv := env.executor.Reader().ProjectVersion()
 			filtered, skippedLines := filterByVersion(string(content), pv)
 			if skippedLines > 0 {
 				t.Logf("Mendix %s: skipped %d version-gated lines", pv.ProductVersion, skippedLines)

mdl/executor/roundtrip_helpers_test.go

@@ -587,7 +587,7 @@ func (e *testEnv) assertContains(createMDL string, expectedProps []string, opts
 // requireMinVersion skips the test if the project's Mendix version is below the given minimum.
 func (e *testEnv) requireMinVersion(t *testing.T, major, minor int) {
 	t.Helper()
-	pv := e.executor.reader.ProjectVersion()
+	pv := e.executor.Reader().ProjectVersion()
 	if !pv.IsAtLeast(major, minor) {
 		t.Skipf("Requires Mendix %d.%d+ (project is %s)", major, minor, pv.ProductVersion)
 	}