fix(root): render Outlet bare for dashboard routes so DashboardChrome isn't nested master
The previous layout-route commit moved DashboardChrome into routes/dashboard/route.tsx but left __root.tsx wrapping everything in ChromeLayout unconditionally. Result: on /dashboard/*, both chromes mounted — ChromeLayout's regular sidebar/header plus DashboardChrome's dashboard sidebar, sitting side by side. (Visible in the screenshot — left 'Streamplace' nav and right 'Creator Dashboard' nav rendered together.) The root still needs to know 'is this a dashboard route' so it can choose to render the Outlet bare (no ChromeLayout) and let the dashboard layout route own the chrome. The isDashboard check is back, but its role is now purely visual: the dashboard layout route always mounts DashboardChrome before its children, so a stale read here just causes a one-frame flash during navigation, not a throw. This should have been part of 55edb157; splitting it into a follow-up so the history shows the iteration honestly.