Docs: question notification actions and the Phase 4 screenshots

docs/api.md

@@ -293,7 +293,7 @@ its body starts with "Subagent <title>:", and its `hostId` and `threadId` are th
 | Category | When | Actions the watch registers |
 | --- | --- | --- |
 | `approval` | A thread needs an approval | Allow (`accept`), Deny (`decline`) |
-| `input` | A thread asked a question | Open |
+| `input` | A thread asked a question | Answer, Open. With `question`: one button per option, Say an answer (text input) when `allowCustomAnswer`, Open |
 | `finished` | A turn completed | Reply (text input), Open |
 | `failed` | A turn failed | Open |
 | `host` | A host's T3 token expires within 7 days, or was rejected | none |