feat: implement mobile terminal UX

- Add mobile viewport detection hook
- Add virtual keyboard detection with fallback
- Add auto-hide hook for header/keys strip
- Add special keys mapping hook
- Create MobileTerminalHeader, SpecialKeysStrip, SpecialKeysPanel components
- Create MobileTerminalWrapper component
- Update TerminalComponent with mobile support, font scaling, copy/paste, reconnection
- Update AppShell to hide chrome on mobile terminal pages
- Update TerminalPage to use MobileTerminalWrapper
- Add comprehensive mobile terminal styles
- TypeScript check passes
- Build succeeds

apps/web/src/hooks/use-mobile-viewport.ts

@@ -0,0 +1,21 @@
+import { useState, useEffect } from "react";
+
+const MOBILE_BREAKPOINT = 768;
+
+export function useMobileViewport() {
+  const [isMobile, setIsMobile] = useState(() => {
+    if (typeof window === "undefined") return false;
+    return window.innerWidth < MOBILE_BREAKPOINT;
+  });
+
+  useEffect(() => {
+    const handleResize = () => {
+      setIsMobile(window.innerWidth < MOBILE_BREAKPOINT);
+    };
+
+    window.addEventListener("resize", handleResize);
+    return () => window.removeEventListener("resize", handleResize);
+  }, []);
+
+  return isMobile;
+}