fix: a modification carries the deck's theme over (the edit the last commit described)

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Dv6sqaY6Vq3ChZHMem3cnU

src/routes/myResources.js

@@ -830,6 +830,9 @@ router.post('/my-resources/:id/refine', async function (req, res) {
       revisedDeck.title = existingDeck.title;
       revisedDeck.subtitle = existingDeck.subtitle;
       revisedDeck.date = existingDeck.date;
+      // The look is the author's, not the model's: a modification never
+      // resets the theme. The column keeps it too, but the two should agree.
+      revisedDeck.theme = existingDeck.theme || existing.theme || revisedDeck.theme;
       // Draw whatever the revised deck asked for, the same way generating does,
       // so each new figure belongs to the slide that wanted it.
       if (sources.wantsImages) {