docs(webhooks): drop poll content arm — not officially supported

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: yanxue06

docs-src/webhooks/events.mdx.vel

@@ -151,7 +151,7 @@ const dedupeKey = `${webhookId}:${payload.message.id}`;
 
 #### Content shapes
 
-`content` is a discriminated union tagged by `type`. Every arm has a fixed wire projection — function thunks (`read()`, `stream()`, async OG accessors) and server-internal fields (filesystem paths) are stripped before delivery, since neither survives `JSON.stringify` nor is useful to a remote handler. The SDK's <TypeTooltip name="Content" type={`{{ content.signature }}`} /> union has 14 published arms today plus two forward-compat arms (`rename`, `avatar`) the worker handles defensively; the two you'll see on the vast majority of inbound deliveries are `text` and `attachment`:
+`content` is a discriminated union tagged by `type`. Every arm has a fixed wire projection — function thunks (`read()`, `stream()`, async OG accessors) and server-internal fields (filesystem paths) are stripped before delivery, since neither survives `JSON.stringify` nor is useful to a remote handler. The SDK's <TypeTooltip name="Content" type={`{{ content.signature }}`} /> union has 12 published arms today plus two forward-compat arms (`rename`, `avatar`) the worker handles defensively; the two you'll see on the vast majority of inbound deliveries are `text` and `attachment`:
 
 ```ts
 type Content =
@@ -268,24 +268,6 @@ Every arm of the `Content` union, post-projection. Hand-written rather than vell
     | `items` | `SerializedInboundMessage[]` | Each item is a full inbound-message projection (recursed). The SDK forbids nested groups. |
   </Accordion>
 
-  <Accordion title="poll" description="A poll definition.">
-    | Field | Type | Description |
-    | --- | --- | --- |
-    | `type` | `"poll"` | Discriminator. |
-    | `title` | `string` | Poll title. |
-    | `options` | `{ title: string }[]` | Available choices. |
-  </Accordion>
-
-  <Accordion title="poll_option" description="A vote on a poll option.">
-    | Field | Type | Description |
-    | --- | --- | --- |
-    | `type` | `"poll_option"` | Discriminator. |
-    | `title` | `string` | Title of the chosen option. |
-    | `option` | `{ title }` | Echo of the option for convenience. |
-    | `poll` | `SerializedPoll` | Full poll context (which one was voted on). |
-    | `selected` | `boolean` | `true` for selected, `false` for deselected. |
-  </Accordion>
-
   <Accordion title="effect" description="An iMessage-style effect wrapping inner content.">
     | Field | Type | Description |
     | --- | --- | --- |