Introduce a shared dialog header style (.unified-dialog-header) in app.css and opt dialog components into the new chrome by updating their header markup. Headers now use unified-dialog-icon and unified-dialog-text elements (and import the matching Lucide icons where needed), which standardizes icon placement, title/eyebrow layout, close button styling and responsive behavior. The Command Palette layout was adjusted to include the new header and its grid rows.
The CSS is explicitly opt-in (so page/section headers remain unchanged) and includes hover/focus styles and a theme-sensitive close color variable. This commit is a UI refactor only — no API or behavior logic changes.
Christoph