feat(config): 统一配置加载入口，启动时校验所有YAML配置

将分散的 config.yml、workflow.yaml、sandbox.yaml 加载逻辑统一到 AppConfig 模型，
启动时一次性校验，失败则 fast-fail。sandbox.py 改为从统一配置取值，消除重复加载。
同时修复 onebot 测试并新增14个统一配置测试（总测试 285→300）。

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

tests/unit/test_sandbox.py

@@ -4,11 +4,16 @@ import os
 import pytest
 from unittest.mock import patch
 
-from kilostar.utils.sandbox import (
+from kilostar.utils.config_loader import (
     SandboxConfig,
     FilesystemPolicy,
     ShellPolicy,
     PythonExecutorPolicy,
+    AppConfig,
+    AppInfo,
+    WorkflowConfig,
+)
+from kilostar.utils.sandbox import (
     validate_path,
     validate_shell_command,
     validate_python_code,
@@ -24,47 +29,49 @@ from kilostar.utils.sandbox import (
 
 @pytest.fixture(autouse=True)
 def reset_sandbox_config():
-    """每个测试前重置沙箱配置缓存。"""
-    import kilostar.utils.sandbox as mod
-    mod._current = None
+    """每个测试前重置配置缓存。"""
+    import kilostar.utils.config_loader as loader
+    loader._app_current = None
     yield
-    mod._current = None
+    loader._app_current = None
 
 
 @pytest.fixture
 def mock_config():
     """注入测试用的沙箱配置。"""
-    import kilostar.utils.sandbox as mod
-    cfg = SandboxConfig(
-        enabled=True,
-        filesystem=FilesystemPolicy(
-            workspace_root="/tmp/kilostar_workspace",
-            allowed_read_paths=["/tmp"],
-            denied_paths=["/etc/shadow", "/root"],
-        ),
-        shell=ShellPolicy(
+    import kilostar.utils.config_loader as loader
+    cfg = AppConfig(
+        sandbox=SandboxConfig(
             enabled=True,
-            blocked_commands=["rm -rf /", "mkfs", "shutdown"],
-            blocked_operators=["&&", "||", ";", "`", "$("],
-            max_timeout=60,
-        ),
-        python_executor=PythonExecutorPolicy(
-            enabled=True,
-            max_timeout=30,
-            blocked_imports=["os", "subprocess", "shutil"],
-            blocked_builtins=["exec", "eval", "__import__"],
+            filesystem=FilesystemPolicy(
+                workspace_root="/tmp/kilostar_workspace",
+                allowed_read_paths=["/tmp"],
+                denied_paths=["/etc/shadow", "/root"],
+            ),
+            shell=ShellPolicy(
+                enabled=True,
+                blocked_commands=["rm -rf /", "mkfs", "shutdown"],
+                blocked_operators=["&&", "||", ";", "`", "$("],
+                max_timeout=60,
+            ),
+            python_executor=PythonExecutorPolicy(
+                enabled=True,
+                max_timeout=30,
+                blocked_imports=["os", "subprocess", "shutil"],
+                blocked_builtins=["exec", "eval", "__import__"],
+            ),
         ),
     )
-    mod._current = cfg
+    loader._app_current = cfg
     return cfg
 
 
 @pytest.fixture
 def disabled_config():
     """沙箱关闭时的配置。"""
-    import kilostar.utils.sandbox as mod
-    cfg = SandboxConfig(enabled=False)
-    mod._current = cfg
+    import kilostar.utils.config_loader as loader
+    cfg = AppConfig(sandbox=SandboxConfig(enabled=False))
+    loader._app_current = cfg
     return cfg
 
 
@@ -140,10 +147,12 @@ class TestValidateShellCommand:
         assert validate_shell_command("rm -rf /") == "rm -rf /"
 
     def test_shell_disabled_in_policy(self):
-        import kilostar.utils.sandbox as mod
-        mod._current = SandboxConfig(
-            enabled=True,
-            shell=ShellPolicy(enabled=False),
+        import kilostar.utils.config_loader as loader
+        loader._app_current = AppConfig(
+            sandbox=SandboxConfig(
+                enabled=True,
+                shell=ShellPolicy(enabled=False),
+            ),
         )
         with pytest.raises(CommandViolation, match="已被沙箱策略禁用"):
             validate_shell_command("ls")
@@ -190,10 +199,12 @@ class TestValidatePythonCode:
         assert validate_python_code("import os") == "import os"
 
     def test_python_disabled_in_policy(self):
-        import kilostar.utils.sandbox as mod
-        mod._current = SandboxConfig(
-            enabled=True,
-            python_executor=PythonExecutorPolicy(enabled=False),
+        import kilostar.utils.config_loader as loader
+        loader._app_current = AppConfig(
+            sandbox=SandboxConfig(
+                enabled=True,
+                python_executor=PythonExecutorPolicy(enabled=False),
+            ),
         )
         with pytest.raises(CodeViolation, match="已被沙箱策略禁用"):
             validate_python_code("print(1)")