test(M00): calibrate paired renderer checkpoints

Work-Package: M00-QAR-VISUAL-DIFF-001
Agent: sindo-main-codex
Tests: synthetic JPG/PNG diff, manifest, coordination and documentation gates
Fidelity: five build 12340 references compared; coordinate and placement gaps recorded

src/tools/verify_render_baseline_manifest.gd

@@ -20,6 +20,8 @@ func _initialize() -> void:
 	_expect(int(manifest.get("schema_version", 0)) == 1, "manifest schema must be version 1", failures)
 	_expect(String(manifest.get("profile", "")) == "Blizzlike335", "manifest profile must be Blizzlike335", failures)
 	_expect(ResourceLoader.exists(String(manifest.get("scene", ""))), "streaming scene must exist", failures)
+	var fidelity_viewport: Array = manifest.get("fidelity_comparison_viewport", [])
+	_expect(fidelity_viewport.size() == 2 and int(fidelity_viewport[0]) > 0 and int(fidelity_viewport[1]) > 0, "fidelity comparison viewport must contain positive width and height", failures)
 
 	var covered := {}
 	var names := {}