docs: update wording around layout.

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: knightedcodemonkey

README.md

@@ -34,7 +34,7 @@ browser acts as the runtime host for editing, render, lint, and typecheck flows.
 - use iframe-isolated preview style encapsulation while iterating
 - connect a GitHub repository and run Open PR / Push Commit workflows
 - use AI chat with tab-aware proposals and apply/undo controls
-- switch layout and theme while preserving fast feedback loops
+- switch theme and collapse the preview panel while preserving fast feedback loops
 
 ## Why this shape