Pre-fetch prompt tools from the agent's toolset, not the caller's

Tool pre-fetch ran the caller's own active tools, so a teammate chatting
with a shared agent had the owner's prompt fill in from their tools, and
even the owner got every active tool rather than the agent's. It now uses
the toolset the run gets: the agent's tools as its owner or sponsor, or
the caller's tools and defaults outside an agent. Pre-fetch asks nobody,
so on someone else's tool it skips approval-gated actions and anything on
a connected account.

tests/api/answer/services/test_stream_processor_utils.py

@@ -22,7 +22,7 @@ def _patch_db(conn):
         "docsgpt.api.answer.services.stream_processor.db_readonly", _yield
     ), patch(
         "docsgpt.api.answer.services.stream_processor.db_session", _yield
-    ):
+    ), patch("docsgpt.agents.tool_executor.db_readonly", _yield):
         yield