refactor(config): eliminate global mutable state, wire DeerFlowContext into runtime

- Freeze all config models (AppConfig + 15 sub-configs) with frozen=True
- Purify from_file() — remove 9 load_*_from_dict() side-effect calls
- Replace mtime/reload/push/pop machinery with single ContextVar + init_app_config()
- Delete 10 sub-module globals and their getters/setters/loaders
- Migrate 50+ consumers from get_*_config() to get_app_config().xxx

- Expand DeerFlowContext: app_config + thread_id + agent_name (frozen dataclass)
- Wire into Gateway runtime (worker.py) and DeerFlowClient via context= parameter
- Remove sandbox_id from runtime.context — flows through ThreadState.sandbox only
- Middleware/tools access runtime.context directly via Runtime[DeerFlowContext] generic
- resolve_context() retained at server entry points for LangGraph Server fallback

backend/tests/test_acp_config.py

@@ -6,17 +6,20 @@ import pytest
 import yaml
 from pydantic import ValidationError
 
-from deerflow.config.acp_config import ACPAgentConfig, get_acp_agents, load_acp_config_from_dict
+from deerflow.config.acp_config import ACPAgentConfig
 from deerflow.config.app_config import AppConfig
+from deerflow.config.sandbox_config import SandboxConfig
 
 
-def setup_function():
-    """Reset ACP config before each test."""
-    load_acp_config_from_dict({})
+def _make_config(acp_agents: dict | None = None) -> AppConfig:
+    return AppConfig(
+        sandbox=SandboxConfig(use="test"),
+        acp_agents={name: ACPAgentConfig(**cfg) for name, cfg in (acp_agents or {}).items()},
+    )
 
 
-def test_load_acp_config_sets_agents():
-    load_acp_config_from_dict(
+def test_acp_agents_via_app_config():
+    cfg = _make_config(
         {
             "claude_code": {
                 "command": "claude-code-acp",
@@ -26,39 +29,33 @@ def test_load_acp_config_sets_agents():
             }
         }
     )
-    agents = get_acp_agents()
+    agents = cfg.acp_agents
     assert "claude_code" in agents
     assert agents["claude_code"].command == "claude-code-acp"
     assert agents["claude_code"].description == "Claude Code for coding tasks"
     assert agents["claude_code"].model is None
 
 
-def test_load_acp_config_multiple_agents():
-    load_acp_config_from_dict(
+def test_multiple_agents():
+    cfg = _make_config(
         {
             "claude_code": {"command": "claude-code-acp", "args": [], "description": "Claude Code"},
             "codex": {"command": "codex-acp", "args": ["--flag"], "description": "Codex CLI"},
         }
     )
-    agents = get_acp_agents()
+    agents = cfg.acp_agents
     assert len(agents) == 2
     assert agents["codex"].args == ["--flag"]
 
 
-def test_load_acp_config_empty_clears_agents():
-    load_acp_config_from_dict({"agent": {"command": "cmd", "args": [], "description": "desc"}})
-    assert len(get_acp_agents()) == 1
-
-    load_acp_config_from_dict({})
-    assert len(get_acp_agents()) == 0
+def test_empty_acp_agents():
+    cfg = _make_config({})
+    assert cfg.acp_agents == {}
 
 
-def test_load_acp_config_none_clears_agents():
-    load_acp_config_from_dict({"agent": {"command": "cmd", "args": [], "description": "desc"}})
-    assert len(get_acp_agents()) == 1
-
-    load_acp_config_from_dict(None)
-    assert get_acp_agents() == {}
+def test_default_acp_agents_empty():
+    cfg = AppConfig(sandbox=SandboxConfig(use="test"))
+    assert cfg.acp_agents == {}
 
 
 def test_acp_agent_config_defaults():
@@ -79,8 +76,8 @@ def test_acp_agent_config_env_default_is_empty():
     assert cfg.env == {}
 
 
-def test_load_acp_config_preserves_env():
-    load_acp_config_from_dict(
+def test_acp_agent_preserves_env():
+    cfg = _make_config(
         {
             "codex": {
                 "command": "codex-acp",
@@ -90,8 +87,7 @@ def test_load_acp_config_preserves_env():
             }
         }
     )
-    cfg = get_acp_agents()["codex"]
-    assert cfg.env == {"OPENAI_API_KEY": "$OPENAI_API_KEY", "FOO": "bar"}
+    assert cfg.acp_agents["codex"].env == {"OPENAI_API_KEY": "$OPENAI_API_KEY", "FOO": "bar"}
 
 
 def test_acp_agent_config_with_model():
@@ -115,13 +111,7 @@ def test_acp_agent_config_missing_description_raises():
         ACPAgentConfig(command="my-agent")
 
 
-def test_get_acp_agents_returns_empty_by_default():
-    """After clearing, should return empty dict."""
-    load_acp_config_from_dict({})
-    assert get_acp_agents() == {}
-
-
-def test_app_config_reload_without_acp_agents_clears_previous_state(tmp_path, monkeypatch):
+def test_app_config_from_file_with_acp_agents(tmp_path, monkeypatch):
     config_path = tmp_path / "config.yaml"
     extensions_path = tmp_path / "extensions_config.json"
     extensions_path.write_text(json.dumps({"mcpServers": {}, "skills": {}}), encoding="utf-8")
@@ -157,9 +147,9 @@ def test_app_config_reload_without_acp_agents_clears_previous_state(tmp_path, mo
     monkeypatch.setenv("DEER_FLOW_EXTENSIONS_CONFIG_PATH", str(extensions_path))
 
     config_path.write_text(yaml.safe_dump(config_with_acp), encoding="utf-8")
-    AppConfig.from_file(str(config_path))
-    assert set(get_acp_agents()) == {"codex"}
+    app = AppConfig.from_file(str(config_path))
+    assert set(app.acp_agents) == {"codex"}
 
     config_path.write_text(yaml.safe_dump(config_without_acp), encoding="utf-8")
-    AppConfig.from_file(str(config_path))
-    assert get_acp_agents() == {}
+    app = AppConfig.from_file(str(config_path))
+    assert app.acp_agents == {}