Web UI doesn't respect tui.diff_style config setting

[ravshansbox]

Web UI ignores the tui.diff_style configuration setting in opencode.json. When setting tui.diff_style to "stacked", the TUI correctly shows unified diff view, but the web UI continues to use split view.

This is inconsistent with expected behavior - the config should control diff view style across all interfaces (TUI and Web UI).

Steps to reproduce:

1. Set tui.diff_style to "stacked" in opencode.json
2. Open TUI - diff view is correctly shown as unified (single column)
3. Open Web UI - diff view still shows split (side-by-side)
4. Expected: Web UI should also show unified diff view when config is set to "stacked"