Joseph Doherty
b09de9b777
Add ThemeShell.razor (regular component, not LayoutComponentBase) with Product, Accent, Logo, Nav, RailFooter, and ChildContent parameters. Accent uses nullable AccentStyle so the style attribute is entirely absent when null. Composes BrandBar inside .side-rail, wraps page in <main class="page">. Add ThemeShellTests.cs (4 tests: product/nav/body, accent sets css var, no-accent emits no style, RailFooter). All 18 tests green, 0 build warnings.