修复测试模型路径并完善四路八路回归与文档

- 按文件哈希区分当前八路工程和历史 Amesim 基准，修复测试与清单中的旧路径。
- 四路审计从 JSON 按需生成 XML，八路新增只核对模式，并显式使用 UTF-8 与 LF。
- 将缺失高刚度夹具的测试替换为当前八路完整 BDF 运行，明确未恢复原 RK45 专项覆盖。
- 更新前端大型工程测试、历史活动回放入口、数据说明、现行规范和相关报告。

验证：全量后台 374 项通过、1 项条件跳过；前端 11 项通过、历史独立服务用例 1 项跳过；四路八路 AME 审计通过。
环境、缓存和运行产物保持忽略；本次未实施工程 JSON 字段精简。

tests/test_current_mql8_simulation.py

@@ -0,0 +1,59 @@
+"""Current eight-branch execution regression.
+
+The deleted high_stiffness_explicit_rk45.xml is not reconstructed or renamed.
+Per the user decision on 2026-09-12, exercise the corrected eight-branch JSON
+through the real XML/native path. This does not claim the former RK45 coverage.
+"""
+from __future__ import annotations
+
+import json
+import math
+import unittest
+from xml.etree import ElementTree as ET
+
+from app.main import run_system_xml_simulation
+from app.simulation.native_codegen.input import load_input
+from app.simulation.paths import CURRENT_MQL8_PROJECT_PATH
+
+
+class CurrentMql8SimulationTests(unittest.TestCase):
+    def test_corrected_eight_branch_runs_its_complete_saved_configuration(self):
+        original = CURRENT_MQL8_PROJECT_PATH.read_bytes()
+        project = json.loads(original)
+        settings = project["simulation"]
+        xml, document = load_input(CURRENT_MQL8_PROJECT_PATH)
+        self.assertEqual(len(document.components), len(project["nodes"]))
+        self.assertEqual(len(document.connections), len(project["edges"]))
+        self.assertEqual(ET.fromstring(xml).get("unitSystem"), "SI")
+        result = run_system_xml_simulation(xml, cancel_check=lambda: False)
+
+        self.assertTrue(result["success"], result["message"])
+        self.assertEqual(result["status"], "completed")
+        self.assertFalse(result["partial"])
+        self.assertEqual(result["simulatedUntil"], settings["t_stop"])
+        integration = result["diagnostics"]["integration"]
+        self.assertEqual(integration["method"], settings["method"])
+        self.assertEqual(integration["rtol"], 1e-8)
+        self.assertEqual(result["diagnostics"]["native"]["backend"], "native-c")
+        # The current case includes a mechanical transition over the complete 10 s.
+        self.assertGreaterEqual(integration["totals"]["stateTransitionCount"], 1)
+        self.assertGreaterEqual(integration["totals"]["solverStartCount"], 2)
+
+        series = result["series"]
+        times = series["time"]
+        self.assertEqual(times[0], settings["t_start"])
+        self.assertEqual(times[-1], settings["t_stop"])
+        self.assertTrue(all(a < b for a, b in zip(times, times[1:])))
+        # Keep every requested output point, in addition to inserted event points.
+        step = settings["step"]
+        actual_grid = {round(t / step) for t in times if abs(t / step - round(t / step)) < 1e-8}
+        expected_grid = set(range(round(settings["t_start"] / step), round(settings["t_stop"] / step) + 1))
+        self.assertTrue(expected_grid.issubset(actual_grid))
+        for key, values in series.items():
+            self.assertEqual(len(values), len(times), key)
+            self.assertTrue(all(math.isfinite(value) for value in values), key)
+        self.assertEqual(CURRENT_MQL8_PROJECT_PATH.read_bytes(), original)
+
+
+if __name__ == "__main__":
+    unittest.main()