feat: antropic model added fix & kb tooling fixes

- Updated main-agent middleware to clarify that both filesystem reads/writes and knowledge-base retrieval are handled by the `knowledge_base` subagent.
- Introduced `_forward_mention_pins` function to carry `@`-mention pins into subagent state.
- Revised system prompts to reflect the new retrieval method and ensure proper citation handling.
- Removed the `search_knowledge_base` tool and its related tests, consolidating functionality under the `task` tool.
- Enhanced documentation to guide usage of the new retrieval approach and citation practices.

surfsense_backend/app/agents/chat/runtime/references/connectors.py

@@ -53,9 +53,7 @@ async def resolve_connector_references(
     )
     accessible = {row.id: row for row in rows.all()}
 
-    chip_by_id = {
-        chip.id: chip for chip in (chips or []) if chip.kind == "connector"
-    }
+    chip_by_id = {chip.id: chip for chip in (chips or []) if chip.kind == "connector"}
 
     references: list[ConnectorReference] = []
     for connector_id in dict.fromkeys(connector_ids):

surfsense_backend/app/agents/chat/runtime/references/models.py

@@ -8,11 +8,11 @@ a class-level discriminator used by the renderer and scope builder.
 from __future__ import annotations
 
 from dataclasses import dataclass
-from enum import Enum
+from enum import StrEnum
 from typing import ClassVar
 
 
-class ReferenceKind(str, Enum):
+class ReferenceKind(StrEnum):
     """What the user pointed at; the value is the label shown to the model."""
 
     DOCUMENT = "document"

surfsense_backend/app/agents/chat/runtime/references/reference_pointers.py

@@ -33,9 +33,7 @@ def render_reference_pointers(references: list[Reference]) -> str | None:
     lines = [_render_pointer(reference) for reference in references]
     return (
         "<referenced_this_turn>\n"
-        f"{_HEADER}\n"
-        + "\n".join(lines)
-        + "\n</referenced_this_turn>"
+        f"{_HEADER}\n" + "\n".join(lines) + "\n</referenced_this_turn>"
     )