refactor(agents): move context schema + state reducers to app/agents/shared (slice 2)

Continue promoting the shared agent toolkit out of `new_chat` into the
cross-agent `app/agents/shared` kernel.

- state_reducers.py: clean move (no single-agent importer); all 7 importers
  flipped to app.agents.shared.state_reducers.
- context.py: moved to app.agents.shared.context; flipped the multi-agent,
  app, automations, chat-flows and monolith importers. A thin re-export shim
  remains at new_chat/context.py because the not-yet-retired single-agent
  (chat_deepagent) and the new_chat package __init__ still import it; the shim
  goes away with the single-agent deletion.
- Updated the stream parity test's annotation normalizer to strip the new
  app.agents.shared.context. prefix (SurfSenseContextSchema.__module__ changed
  with the move), keeping monolith<->flows signature parity intact.

Behavior-preserving: definitions unchanged; only import paths move. 1219 tests green.

surfsense_backend/app/agents/shared/context.py

@@ -0,0 +1,71 @@
+"""
+Context schema definitions for SurfSense agents.
+
+This module defines the per-invocation context object passed to the SurfSense
+deep agent via ``agent.astream_events(..., context=ctx)`` (LangGraph >= 0.6).
+
+The agent's compiled graph is the same across invocations (and cached by
+``agent_cache``), so anything that varies per turn — the user mentions a
+specific document, the front-end issues a unique ``request_id``, etc. —
+MUST live on this context object instead of being captured into a
+middleware ``__init__`` closure. Middlewares read fields back via
+``runtime.context.<field>``; tools read them via ``runtime.context``.
+
+This object is read inside both ``KnowledgePriorityMiddleware`` (for
+``mentioned_document_ids``) and any future middleware that needs
+per-request state without invalidating the compiled-agent cache.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import TypedDict
+
+
+class FileOperationContractState(TypedDict):
+    intent: str
+    confidence: float
+    suggested_path: str
+    timestamp: str
+    turn_id: str
+
+
+@dataclass
+class SurfSenseContextSchema:
+    """
+    Per-invocation context for the SurfSense deep agent.
+
+    Defaults are chosen so the dataclass can be safely default-constructed
+    (LangGraph's ``Runtime.context`` itself defaults to ``None`` if no
+    context is supplied — see ``langgraph.runtime.Runtime``). All fields
+    are optional; consumers must None-check before reading.
+
+    Phase 1.5 fields:
+        search_space_id: Search space the request is scoped to.
+        mentioned_document_ids: KB documents the user @-mentioned this turn.
+            Read by ``KnowledgePriorityMiddleware`` to seed its priority
+            list. Stays out of the compiled-agent cache key — that's the
+            whole point of putting it here.
+        mentioned_folder_ids: KB folders the user @-mentioned this turn
+            (cloud filesystem mode). Surfaced as ``[USER-MENTIONED]``
+            entries in ``<priority_documents>`` so the agent prioritises
+            walking those folders with ``ls`` / ``find_documents``.
+        file_operation_contract: One-shot file operation contract emitted
+            by ``FileIntentMiddleware`` for the upcoming turn.
+        turn_id / request_id: Correlation IDs surfaced by the streaming
+            task; populated for telemetry.
+
+    Phase 2 will extend with: thread_id, user_id, visibility,
+    filesystem_mode, anon_session_id, available_connectors,
+    available_document_types, created_by_id (everything currently captured
+    by middleware ``__init__`` closures).
+    """
+
+    search_space_id: int | None = None
+    mentioned_document_ids: list[int] = field(default_factory=list)
+    mentioned_folder_ids: list[int] = field(default_factory=list)
+    mentioned_connector_ids: list[int] = field(default_factory=list)
+    mentioned_connectors: list[dict[str, object]] = field(default_factory=list)
+    file_operation_contract: FileOperationContractState | None = None
+    turn_id: str | None = None
+    request_id: str | None = None