Fix Chat Interactions shows "!caption" text instead of preview images when an answer also offers a download

[JackTelford]

Fixes #235

The bug

On the MVC sample's Chat Interactions page, an answer that both previews a document and offers it as a download showed the preview captions as plain text with a stray ! (!Slide 9: Executive Summary: Key KPIs) instead of the images. It affected the PowerPoint, Word and PDF agents alike. Previews without a download rendered fine, which made it look intermittent.

Why it happened

Chat.cshtml has its own inline rendering pipeline:

1. expandImageMarkers turns [fig:N] into ![caption](/ai/documents/{id}/download).
2. When the message carries download references, replaceGeneratedMarkdownLinks rewrites markdown links with /\[([^\]]+)\]\(([^)]+)\)/g.
3. That pattern also matched the [caption](url) inside the image syntax. The image matched no download, so it was replaced by its label, leaving !caption as text before markdown ran.

The fix

The pattern now also captures an optional leading !. When it is present, the match is image markdown and is returned untouched. Ordinary links are handled exactly as before.

return content.replace(/(!?)\[([^\]]+)\]\(([^)]+)\)/g, function (match, imagePrefix, label, url) {
    if (imagePrefix) {
        return match;
    }
    // unchanged link handling
});

Scope

• One function in src/Startup/CrestApps.Core.Mvc.Web/Areas/ChatInteractions/Views/ChatInteraction/Chat.cshtml.
• The shared ai-chat.js and chat-interaction.js never had this function and are unchanged.
• No library package changes, so CrestApps.OrchardCore is unaffected.
• Existing messages render correctly after the fix, since the stored content was never wrong.

How to test

In a Chat Interaction with the presentation tools, send:

Create a 3-slide deck titled "Repro Test": a title slide, one slide with a column chart of Q1=10, Q2=20, Q3=15, and a closing slide. In this same reply, show me a preview of all 3 slides and give me the .pptx download.

Expected: the slide previews render as an image carousel, and the .pptx link appears below them. The same check applies to Word (.docx) and PDF (.pdf).

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