Add Slack app screenshot to the Neo Slack integration page (#19901)

* Add Slack app screenshot to the Neo Slack integration page

Adds a bordered screenshot of a Neo conversation in a Slack thread,
placed right before the "Setting up the integration" section.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Constrain Slack screenshot to 80% width, centered

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: aminix

content/docs/ai/integrations/slack/_index.md

@@ -17,6 +17,8 @@ Mention `@Neo` in any channel where Neo has been added to start a Neo [task](/do
 
 Neo has the same capabilities it does anywhere else: it can check stack state, investigate failures, walk through what a change will do, and carry out actions the team has agreed on. The difference is that the conversation happens in a Slack thread instead of the Pulumi Cloud console, which means the rest of the channel has visibility into what was asked and what Neo found.
 
+<img src="neo-slack-conversation.png" alt="Neo answering a question about a stack's resources in a Slack thread" style="display: block; margin: 0 auto; width: 80%;">
+
 ## Setting up the integration
 
 ### 1. Install the Pulumi Neo Slack app