Replace the sparse start/settings cards with a Win95-styled launcher:
- Start screen is now a 'Welcome to Windows 95' dialog with a gradient
side stripe, a rotating tip box, and a button column.
- Settings is a tabbed Properties sheet (Floppy / Network / State) with
group boxes, sunken read-only path fields, and OK/Cancel.
- Vendored 98.css and its Pixelated MS Sans Serif fonts; dropped the
old 95css-based .btn/.card/.nav classes.
- Removed the bottom taskbar nav (start-menu.tsx) — navigation now goes
through the dialog buttons so the launcher isn't mistaken for the
running OS.