refactor(beaver): 移除Hermes相关引用和迁移代码，完善Beaver后端主线实现

移除了所有Hermes相关的命名引用，包括：
- 从.gitignore中清理相关构建缓存文件
- 将README中的beaver-home路径配置更新
- 完善backend/README.md文档说明Beaver后端主线实现
- 移除Hermes风格的相关注释和兼容性代码
- 清理nanobot环境变量兼容性处理
- 删除技能迁移和服务迁移相关功能代码
- 更新测试用例中相关命名和函数名

BREAKING CHANGE: 移除了Hermes迁移相关API和CLI命令，不再支持nanobot环境变量兼容性

app-instance/backend/tests/unit/test_config_loader.py

@@ -1,5 +1,4 @@
 import json
-from pathlib import Path
 
 from beaver.engine import AgentLoop, EngineLoader
 from beaver.engine.providers import make_provider_bundle
@@ -139,9 +138,36 @@ def test_openai_compatible_qwen_config_keeps_openai_provider() -> None:
     assert bundle.main_provider._resolve_model("qwen-plus") == "openai/qwen-plus"
 
 
-def test_load_config_reads_stevenli_mcp_authz_identity() -> None:
-    repo_root = Path(__file__).resolve().parents[4]
-    config_path = repo_root / "app-instance" / "runtime" / "instances" / "stevenli" / "nanobot-home" / "config.json"
+def test_load_config_reads_mcp_authz_identity(tmp_path) -> None:
+    config_path = tmp_path / "beaver-home" / "config.json"
+    config_path.parent.mkdir()
+    config_path.write_text(
+        json.dumps(
+            {
+                "tools": {
+                    "mcpServers": {
+                        "outlook_mcp": {
+                            "url": "http://10.6.80.29:8000/mcp",
+                            "authMode": "oauth_backend_token",
+                            "authAudience": "mcp:outlook_mcp",
+                            "authScopes": ["list_tools", "tool:mail_list_messages"],
+                            "toolTimeout": 60,
+                            "sensitive": True,
+                        }
+                    }
+                },
+                "authz": {
+                    "enabled": True,
+                    "baseUrl": "http://nano-authz-service:19090",
+                },
+                "backend_identity": {
+                    "backend_id": "stevenli",
+                    "client_id": "stevenli",
+                },
+            }
+        ),
+        encoding="utf-8",
+    )
     config = load_config(config_path=config_path)
 
     server = config.tools.mcp_servers["outlook_mcp"]