refactor(agents): move tools package to app/agents/shared (slice 6)

Relocate the entire new_chat/tools/ package (62 files incl. registry, hitl, MCP
cluster, and all connector subpackages: gmail/slack/discord/teams/drive/etc.)
to the shared kernel. The package turned out to be a clean cohesive cluster:
its only references to non-tools new_chat modules were comments, and its
middleware deps were already flipped to shared in slice 5c.

Flip 33 live importers (multi-agent, flows, routes, services, anonymous_agent,
tests). Re-export shims remain for the frozen single-agent stack: a package
__init__ mirroring the public surface (new_chat.__init__ imports it) plus
invalid_tool + registry submodule shims (chat_deepagent imports those).

Resolves slice 5c's two transient back-edges: shared/middleware/action_log
(TYPE_CHECKING ToolDefinition) and tool_call_repair (local INVALID_TOOL_NAME)
now point at app.agents.shared.tools.

surfsense_backend/tests/e2e/fakes/mcp_runtime.py

@@ -137,10 +137,10 @@ def install(active_patches: list[Any]) -> None:
     """Patch production MCP streamable-HTTP boundaries exactly once."""
     targets = [
         (
-            "app.agents.new_chat.tools.mcp_tool.streamablehttp_client",
+            "app.agents.shared.tools.mcp_tool.streamablehttp_client",
             _fake_streamablehttp_client,
         ),
-        ("app.agents.new_chat.tools.mcp_tool.ClientSession", _FakeClientSession),
+        ("app.agents.shared.tools.mcp_tool.ClientSession", _FakeClientSession),
     ]
     for target, replacement in targets:
         p = patch(target, replacement)