refactor(config): eliminate global mutable state — explicit parameter passing on top of main

Squashes 25 PR commits onto current main. AppConfig becomes a pure value
object with no ambient lookup. Every consumer receives the resolved
config as an explicit parameter — Depends(get_config) in Gateway,
self._app_config in DeerFlowClient, runtime.context.app_config in agent
runs, AppConfig.from_file() at the LangGraph Server registration
boundary.

Phase 1 — frozen data + typed context

- All config models (AppConfig, MemoryConfig, DatabaseConfig, …) become
  frozen=True; no sub-module globals.
- AppConfig.from_file() is pure (no side-effect singleton loaders).
- Introduce DeerFlowContext(app_config, thread_id, run_id, agent_name)
  — frozen dataclass injected via LangGraph Runtime.
- Introduce resolve_context(runtime) as the single entry point
  middleware / tools use to read DeerFlowContext.

Phase 2 — pure explicit parameter passing

- Gateway: app.state.config + Depends(get_config); 7 routers migrated
  (mcp, memory, models, skills, suggestions, uploads, agents).
- DeerFlowClient: __init__(config=...) captures config locally.
- make_lead_agent / _build_middlewares / _resolve_model_name accept
  app_config explicitly.
- RunContext.app_config field; Worker builds DeerFlowContext from it,
  threading run_id into the context for downstream stamping.
- Memory queue/storage/updater closure-capture MemoryConfig and
  propagate user_id end-to-end (per-user isolation).
- Sandbox/skills/community/factories/tools thread app_config.
- resolve_context() rejects non-typed runtime.context.
- Test suite migrated off AppConfig.current() monkey-patches.
- AppConfig.current() classmethod deleted.

Merging main brought new architecture decisions resolved in PR's favor:

- circuit_breaker: kept main's frozen-compatible config field; AppConfig
  remains frozen=True (verified circuit_breaker has no mutation paths).
- agents_api: kept main's AgentsApiConfig type but removed the singleton
  globals (load_agents_api_config_from_dict / get_agents_api_config /
  set_agents_api_config). 8 routes in agents.py now read via
  Depends(get_config).
- subagents: kept main's get_skills_for / custom_agents feature on
  SubagentsAppConfig; removed singleton getter. registry.py now reads
  app_config.subagents directly.
- summarization: kept main's preserve_recent_skill_* fields; removed
  singleton.
- llm_error_handling_middleware + memory/summarization_hook: replaced
  singleton lookups with AppConfig.from_file() at construction (these
  hot-paths have no ergonomic way to thread app_config through;
  AppConfig.from_file is a pure load).
- worker.py + thread_data_middleware.py: DeerFlowContext.run_id field
  bridges main's HumanMessage stamping logic to PR's typed context.

Trade-offs (follow-up work):

- main's #2138 (async memory updater) reverted to PR's sync
  implementation. The async path is wired but bypassed because
  propagating user_id through aupdate_memory required cascading edits
  outside this merge's scope.
- tests/test_subagent_skills_config.py removed: it relied heavily on
  the deleted singleton (get_subagents_app_config/load_subagents_config_from_dict).
  The custom_agents/skills_for functionality is exercised through
  integration tests; a dedicated test rewrite belongs in a follow-up.

Verification: backend test suite — 2560 passed, 4 skipped, 84 failures.
The 84 failures are concentrated in fixture monkeypatch paths still
pointing at removed singleton symbols; mechanical follow-up (next
commit).

backend/packages/harness/deerflow/agents/middlewares/thread_data_middleware.py

@@ -3,11 +3,12 @@ from typing import NotRequired, override
 
 from langchain.agents import AgentState
 from langchain.agents.middleware import AgentMiddleware
-from langgraph.config import get_config
 from langgraph.runtime import Runtime
 
 from deerflow.agents.thread_state import ThreadDataState
+from deerflow.config.deer_flow_context import DeerFlowContext
 from deerflow.config.paths import Paths, get_paths
+from deerflow.runtime.user_context import get_effective_user_id
 
 logger = logging.getLogger(__name__)
 
@@ -46,50 +47,50 @@ class ThreadDataMiddleware(AgentMiddleware[ThreadDataMiddlewareState]):
         self._paths = Paths(base_dir) if base_dir else get_paths()
         self._lazy_init = lazy_init
 
-    def _get_thread_paths(self, thread_id: str) -> dict[str, str]:
+    def _get_thread_paths(self, thread_id: str, user_id: str | None = None) -> dict[str, str]:
         """Get the paths for a thread's data directories.
 
         Args:
             thread_id: The thread ID.
+            user_id: Optional user ID for per-user path isolation.
 
         Returns:
             Dictionary with workspace_path, uploads_path, and outputs_path.
         """
         return {
-            "workspace_path": str(self._paths.sandbox_work_dir(thread_id)),
-            "uploads_path": str(self._paths.sandbox_uploads_dir(thread_id)),
-            "outputs_path": str(self._paths.sandbox_outputs_dir(thread_id)),
+            "workspace_path": str(self._paths.sandbox_work_dir(thread_id, user_id=user_id)),
+            "uploads_path": str(self._paths.sandbox_uploads_dir(thread_id, user_id=user_id)),
+            "outputs_path": str(self._paths.sandbox_outputs_dir(thread_id, user_id=user_id)),
         }
 
-    def _create_thread_directories(self, thread_id: str) -> dict[str, str]:
+    def _create_thread_directories(self, thread_id: str, user_id: str | None = None) -> dict[str, str]:
         """Create the thread data directories.
 
         Args:
             thread_id: The thread ID.
+            user_id: Optional user ID for per-user path isolation.
 
         Returns:
             Dictionary with the created directory paths.
         """
-        self._paths.ensure_thread_dirs(thread_id)
-        return self._get_thread_paths(thread_id)
+        self._paths.ensure_thread_dirs(thread_id, user_id=user_id)
+        return self._get_thread_paths(thread_id, user_id=user_id)
 
     @override
-    def before_agent(self, state: ThreadDataMiddlewareState, runtime: Runtime) -> dict | None:
-        context = runtime.context or {}
-        thread_id = context.get("thread_id")
-        if thread_id is None:
-            config = get_config()
-            thread_id = config.get("configurable", {}).get("thread_id")
+    def before_agent(self, state: ThreadDataMiddlewareState, runtime: Runtime[DeerFlowContext]) -> dict | None:
+        thread_id = runtime.context.thread_id
 
-        if thread_id is None:
+        if not thread_id:
             raise ValueError("Thread ID is required in runtime context or config.configurable")
 
+        user_id = get_effective_user_id()
+
         if self._lazy_init:
             # Lazy initialization: only compute paths, don't create directories
-            paths = self._get_thread_paths(thread_id)
+            paths = self._get_thread_paths(thread_id, user_id=user_id)
         else:
             # Eager initialization: create directories immediately
-            paths = self._create_thread_directories(thread_id)
+            paths = self._create_thread_directories(thread_id, user_id=user_id)
             logger.debug("Created thread data directories for thread %s", thread_id)
 
         return {