refactor(agents): move feature flags to app/agents/shared/feature_flags (slice 2b)

Promote the agent feature-flag resolver (AgentFeatureFlags / get_flags) out of
`new_chat` into the cross-agent `app/agents/shared` kernel.

feature_flags is a pure leaf consumed across the multi-agent middleware stack,
the chat routes, and tests. Moved it via git mv (content unchanged) and flipped
all 37 importers to app.agents.shared.feature_flags. A thin re-export shim
remains at new_chat/feature_flags.py only for the not-yet-retired single-agent
(chat_deepagent); it goes away with the single-agent deletion.

Behavior-preserving: only import paths change. 1243 tests green.

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/action_log.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 import logging
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import ActionLogMiddleware
 from app.agents.new_chat.tools.registry import BUILTIN_TOOLS
 

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/busy_mutex.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import BusyMutexMiddleware
 
 from ..shared.flags import enabled

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/context_editing.py

@@ -10,7 +10,7 @@ from langchain_core.tools import BaseTool
 from app.agents.multi_agent_chat.main_agent.context_prune.prune_tool_names import (
     safe_exclude_tools,
 )
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import (
     ClearToolUsesEdit,
     SpillingContextEditingMiddleware,

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/doom_loop.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import DoomLoopMiddleware
 
 from ..shared.flags import enabled

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/noop_injection.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import NoopInjectionMiddleware
 
 from ..shared.flags import enabled

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/otel.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import OtelSpanMiddleware
 
 from ..shared.flags import enabled

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/plugins.py

@@ -7,7 +7,7 @@ from typing import Any
 
 from langchain_core.language_models import BaseChatModel
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.plugin_loader import (
     PluginContext,
     load_allowed_plugin_names_from_env,

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/repair.py

@@ -6,7 +6,7 @@ from collections.abc import Sequence
 
 from langchain_core.tools import BaseTool
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import ToolCallNameRepairMiddleware
 
 from ..shared.flags import enabled

surfsense_backend/app/agents/multi_agent_chat/middleware/main_agent/skills.py

@@ -6,7 +6,7 @@ import logging
 
 from deepagents.middleware.skills import SkillsMiddleware
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.filesystem_selection import FilesystemMode
 from app.agents.new_chat.middleware import (
     build_skills_backend_factory,

surfsense_backend/app/agents/multi_agent_chat/middleware/shared/flags.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 
 
 def enabled(flags: AgentFeatureFlags, attr: str) -> bool:

surfsense_backend/app/agents/multi_agent_chat/middleware/shared/permissions/middleware/factory.py

@@ -27,7 +27,7 @@ from collections.abc import Sequence
 
 from langchain_core.tools import BaseTool
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.permissions import Rule, Ruleset
 from app.services.user_tool_allowlist import TrustedToolSaver
 

surfsense_backend/app/agents/multi_agent_chat/middleware/shared/resilience/bundle.py

@@ -10,7 +10,7 @@ from langchain.agents.middleware import (
     ToolCallLimitMiddleware,
 )
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import RetryAfterMiddleware
 from app.agents.new_chat.middleware.scoped_model_fallback import (
     ScopedModelFallbackMiddleware,

surfsense_backend/app/agents/multi_agent_chat/middleware/shared/resilience/fallback.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 import logging
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware.scoped_model_fallback import (
     ScopedModelFallbackMiddleware,
 )

surfsense_backend/app/agents/multi_agent_chat/middleware/shared/resilience/model_call_limit.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 from langchain.agents.middleware import ModelCallLimitMiddleware
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 
 from ..flags import enabled
 

surfsense_backend/app/agents/multi_agent_chat/middleware/shared/resilience/retry.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.middleware import RetryAfterMiddleware
 
 from ..flags import enabled

surfsense_backend/app/agents/multi_agent_chat/middleware/shared/resilience/tool_call_limit.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 from langchain.agents.middleware import ToolCallLimitMiddleware
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 
 from ..flags import enabled
 

surfsense_backend/app/agents/multi_agent_chat/middleware/stack.py

@@ -31,7 +31,7 @@ from app.agents.multi_agent_chat.subagents.builtins.knowledge_base.agent import
 from app.agents.multi_agent_chat.subagents.builtins.knowledge_base.ask_knowledge_base_tool import (
     build_ask_knowledge_base_tool,
 )
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 from app.agents.new_chat.filesystem_selection import FilesystemMode
 from app.db import ChatVisibility
 

surfsense_backend/app/agents/multi_agent_chat/middleware/subagent/middleware_stack.py

@@ -14,7 +14,7 @@ from __future__ import annotations
 
 from typing import Any
 
-from app.agents.new_chat.feature_flags import AgentFeatureFlags
+from app.agents.shared.feature_flags import AgentFeatureFlags
 
 from ..shared.permissions import build_permission_mw
 from ..shared.resilience import ResilienceMiddlewares