feat(connectors): put the trigger approval under Propose triggers

The approval mode of proposed triggers sat at the bottom of the
connection page, after roles, channels and pairing, and was easy to
miss. Show it as an option of the permission Propose triggers: nested
and indented, greyed with a reason while the permission is off, with
its limits in a closed Limits list. The row says the current choice
("Proposals: asks first") without opening anything. The bottom section
is gone; an older host with no capability list still shows it as one
block. The saved approval object does not change.

Assisted-by: Claude:claude-sonnet-5-5

docs/content/features/chats-connectors.md

@@ -666,7 +666,9 @@ trigger stays in Studio. Nothing runs before the owner confirms.
 ### Approval modes
 
 The owner chooses, per binding, what happens to a proposal. The choice is on the settings
-page of the connector add-on, or in the `approval` field of the binding
+page of the connector add-on, nested under the permission **Propose triggers** (greyed while
+that permission is off, with its limits in a closed **Limits** list, and the current mode in
+the line of the row), or in the `approval` field of the binding
 (`PUT /api/chats/connectors/{id}`), and is the same for every connector.
 
 | `mode` | Behavior |