Simplify Admin > Connectors

- One control for members' own MCP servers: the custom MCP server row's
  switch (it sets both the policy and the instance switch); the separate
  top-level switch is gone.
- Connectors that only sync content show "No tools" instead of a
  sharing policy, and the policies read "The sharer decides per share",
  "Always the sharer's account", "Always each person's own account".
- A connector that needs server settings can't be switched on until they
  exist; a tooltip says why.
- On phones the table becomes a list ("On · 2 connections · …") and each
  connector's controls open in a sheet.

docsgpt/api/admin/connectors.py

@@ -70,6 +70,7 @@ class AdminConnectorsResource(Resource):
                     "category": definition.category,
                     "publisher": definition.publisher,
                     "auth_kind": definition.auth_kind,
+                    "capabilities": list(definition.capabilities),
                     "enabled": service.connector_is_enabled(policies, definition.key),
                     "credential_mode": policy.get("credential_mode", "choose"),
                     "configured": definition.configured,