feat: add font size controls to mobile terminal header and fix auto-hide space reclamation

- TerminalComponent: expose changeFontSize via onTerminalReady callback
- MobileTerminalWrapper: pass changeFontSize to header
- MobileTerminalHeader: add A- and A+ font size buttons
- CSS: collapse header height/padding/margin/border when hidden to reclaim space

apps/web/src/components/terminal.tsx

@@ -15,7 +15,8 @@ interface TerminalProps {
   onTerminalReady?: (
     sendData: (data: string) => void,
     connectionStatus: "connecting" | "connected" | "disconnected" | "error",
-    focusInput: () => void
+    focusInput: () => void,
+    changeFontSize: (delta: number) => void
   ) => void;
 }
 
@@ -219,7 +220,10 @@ export const TerminalComponent: React.FC<TerminalProps> = ({
       const focusInput = () => {
         termRef.current?.focus();
       };
-      onTerminalReadyRef.current(sendData, status, focusInput);
+      const changeFontSize = (delta: number) => {
+        handleFontSizeChange(delta);
+      };
+      onTerminalReadyRef.current(sendData, status, focusInput, changeFontSize);
     }
 
     // Visibility API for reconnection
@@ -251,7 +255,10 @@ export const TerminalComponent: React.FC<TerminalProps> = ({
       const focusInput = () => {
         termRef.current?.focus();
       };
-      onTerminalReady(sendData, status, focusInput);
+      const changeFontSize = (delta: number) => {
+        handleFontSizeChange(delta);
+      };
+      onTerminalReady(sendData, status, focusInput, changeFontSize);
     }
   }, [status, onTerminalReady]);