Gateway: multi-select answers and a summary endpoint for the complication

docs/api.md

@@ -89,7 +89,7 @@ PendingRequest {
 
 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 }`.
+`{ id, header, question, options: [{ label, value }], allowCustomAnswer, multiSelect }`.
 
 ## Thread
 
@@ -118,11 +118,27 @@ or
 202
 ```
 
+Each answer is an option `value` or a typed answer. For a question with `multiSelect: true`, send an
+array of option values instead, for example `{ "<questionId>": ["sqlite", "postgres"] }`.
+
 ```
 POST /v1/threads/:hostId/:threadId/stop
 202
 ```
 
+## Summary
+
+The counts behind the watch face complication. It reads no thread pages, so it is cheap to call.
+
+```
+GET /v1/summary
+
+200 { "needsYou": 1, "working": 3, "hostsOffline": 0,
+      "next": { "hostId": "...", "threadId": "...", "title": "Receipt OCR", "hostLabel": "Mac mini" } }
+```
+
+`next` is the thread that has waited longest for you, or null.
+
 ## New thread
 
 ```