Contract: pass approval option warnings, omit threadId on host pushes

docs/api.md

@@ -87,7 +87,8 @@ PendingRequest {
 }
 ```
 
-For questions (`kind: "user_input"`), `options` is empty and `questions` lists
+An option may also carry `warning`, a short note about a risky choice such as "Applies to every
+thread". For questions (`kind: "user_input"`), `options` is empty and `questions` lists
 `{ id, header, question, options: [{ label, value }], allowCustomAnswer }`.
 
 ## Thread
@@ -145,8 +146,8 @@ The new thread uses the project's default model, or the host's, and the host's d
 ## Notifications
 
 The gateway pushes when a thread starts waiting for you, finishes, or fails. Each push has an
-`aps.category` and the custom keys `hostId`, `threadId`, and, for approvals and questions,
-`requestId`.
+`aps.category` and the custom keys `hostId`, `threadId` (absent on `host` pushes), and, for
+approvals and questions, `requestId`.
 
 | Category | When | Actions the watch registers |
 | --- | --- | --- |