refactor(agents): colocate 8 main-agent-only middleware as per-concept folders

Each main-agent-only middleware now lives in its own folder under
main_agent/middleware/<concept>/ with builder.py (flag-gated construction)
+ middleware.py (the impl), re-exported via __init__.py. This kills the
cross-folder hop into agents/shared/middleware and keeps each middleware's
two responsibilities (build vs behavior) as colocated siblings.

Moved (impl from shared/middleware, builder from main_agent/middleware):
action_log, anonymous_document, context_editing, doom_loop, knowledge_tree,
noop_injection, otel_span, tool_call_repair.

Impls moved verbatim (git rename, no body edits) so behavior is unchanged.
Builders now import from the local .middleware sibling. stack.py import
paths updated for the 3 renamed folders; shared middleware barrel trimmed;
tests repointed (imports + patch targets).

surfsense_backend/tests/unit/agents/new_chat/test_action_log.py

@@ -10,9 +10,11 @@ import pytest
 from langchain_core.messages import ToolMessage
 from langchain_core.tools import tool
 
+from app.agents.multi_agent_chat.main_agent.middleware.action_log.middleware import (
+    ActionLogMiddleware,
+    ToolDefinition,
+)
 from app.agents.shared.feature_flags import AgentFeatureFlags
-from app.agents.shared.middleware.action_log import ActionLogMiddleware
-from app.agents.shared.middleware.action_log import ToolDefinition
 
 
 @dataclass
@@ -58,7 +60,7 @@ def _disabled_flags() -> AgentFeatureFlags:
 def patch_get_flags():
     def _patch(flags: AgentFeatureFlags):
         return patch(
-            "app.agents.shared.middleware.action_log.get_flags",
+            "app.agents.multi_agent_chat.main_agent.middleware.action_log.middleware.get_flags",
             return_value=flags,
         )
 
@@ -360,7 +362,7 @@ class TestActionLogDispatch:
             patch_get_flags(_enabled_flags()),
             patch("app.db.shielded_async_session", side_effect=lambda: factory()),
             patch(
-                "app.agents.shared.middleware.action_log.adispatch_custom_event",
+                "app.agents.multi_agent_chat.main_agent.middleware.action_log.middleware.adispatch_custom_event",
                 dispatch_mock,
             ),
         ):
@@ -395,7 +397,7 @@ class TestActionLogDispatch:
             patch_get_flags(_enabled_flags()),
             patch("app.db.shielded_async_session", side_effect=_exploding_session),
             patch(
-                "app.agents.shared.middleware.action_log.adispatch_custom_event",
+                "app.agents.multi_agent_chat.main_agent.middleware.action_log.middleware.adispatch_custom_event",
                 dispatch_mock,
             ),
         ):

surfsense_backend/tests/unit/agents/new_chat/test_context_editing.py

@@ -7,7 +7,7 @@ from typing import Any
 import pytest
 from langchain_core.messages import AIMessage, HumanMessage, ToolMessage
 
-from app.agents.shared.middleware.context_editing import (
+from app.agents.multi_agent_chat.main_agent.middleware.context_editing.middleware import (
     SpillToBackendEdit,
     _build_spill_placeholder,
 )

surfsense_backend/tests/unit/agents/new_chat/test_doom_loop.py

@@ -5,7 +5,10 @@ from __future__ import annotations
 import pytest
 from langchain_core.messages import AIMessage
 
-from app.agents.shared.middleware.doom_loop import DoomLoopMiddleware, _signature
+from app.agents.multi_agent_chat.main_agent.middleware.doom_loop.middleware import (
+    DoomLoopMiddleware,
+    _signature,
+)
 
 pytestmark = pytest.mark.unit
 

surfsense_backend/tests/unit/agents/new_chat/test_noop_injection.py

@@ -5,7 +5,7 @@ from __future__ import annotations
 import pytest
 from langchain_core.messages import AIMessage, HumanMessage
 
-from app.agents.shared.middleware.noop_injection import (
+from app.agents.multi_agent_chat.main_agent.middleware.noop_injection.middleware import (
     NOOP_TOOL_NAME,
     NoopInjectionMiddleware,
     _last_ai_has_tool_calls,

surfsense_backend/tests/unit/agents/new_chat/test_otel_span.py

@@ -8,7 +8,7 @@ from unittest.mock import MagicMock
 import pytest
 from langchain_core.messages import AIMessage, ToolMessage
 
-from app.agents.shared.middleware.otel_span import (
+from app.agents.multi_agent_chat.main_agent.middleware.otel_span.middleware import (
     OtelSpanMiddleware,
     _annotate_model_response,
     _annotate_tool_result,
@@ -206,13 +206,13 @@ class TestMiddlewareIntegration:
         duration_calls: list[dict[str, Any]] = []
         token_calls: list[dict[str, Any]] = []
         monkeypatch.setattr(
-            "app.agents.shared.middleware.otel_span.ot_metrics.record_model_call_duration",
+            "app.agents.multi_agent_chat.main_agent.middleware.otel_span.middleware.ot_metrics.record_model_call_duration",
             lambda duration_ms, **attrs: duration_calls.append(
                 {"duration_ms": duration_ms, **attrs}
             ),
         )
         monkeypatch.setattr(
-            "app.agents.shared.middleware.otel_span.ot_metrics.record_model_token_usage",
+            "app.agents.multi_agent_chat.main_agent.middleware.otel_span.middleware.ot_metrics.record_model_token_usage",
             lambda **attrs: token_calls.append(attrs),
         )
 
@@ -257,11 +257,11 @@ class TestMiddlewareIntegration:
 
         errors: list[str] = []
         monkeypatch.setattr(
-            "app.agents.shared.middleware.otel_span.ot_metrics.record_tool_call_error",
+            "app.agents.multi_agent_chat.main_agent.middleware.otel_span.middleware.ot_metrics.record_tool_call_error",
             lambda *, tool_name: errors.append(tool_name),
         )
         monkeypatch.setattr(
-            "app.agents.shared.middleware.otel_span.ot_metrics.record_tool_call_duration",
+            "app.agents.multi_agent_chat.main_agent.middleware.otel_span.middleware.ot_metrics.record_tool_call_duration",
             lambda *args, **kwargs: None,
         )
 

surfsense_backend/tests/unit/agents/new_chat/test_tool_call_repair.py

@@ -5,10 +5,10 @@ from __future__ import annotations
 import pytest
 from langchain_core.messages import AIMessage
 
-from app.agents.multi_agent_chat.main_agent.tools.invalid_tool import INVALID_TOOL_NAME
-from app.agents.shared.middleware.tool_call_repair import (
+from app.agents.multi_agent_chat.main_agent.middleware.tool_call_repair.middleware import (
     ToolCallNameRepairMiddleware,
 )
+from app.agents.multi_agent_chat.main_agent.tools.invalid_tool import INVALID_TOOL_NAME
 
 pytestmark = pytest.mark.unit
 

surfsense_backend/tests/unit/middleware/test_knowledge_tree.py

@@ -9,7 +9,9 @@ contract cannot silently regress.
 
 from __future__ import annotations
 
-from app.agents.shared.middleware.knowledge_tree import KnowledgeTreeMiddleware
+from app.agents.multi_agent_chat.main_agent.middleware.knowledge_tree.middleware import (
+    KnowledgeTreeMiddleware,
+)
 from app.agents.shared.path_resolver import DOCUMENTS_ROOT