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/styles.css

@@ -2960,19 +2960,28 @@ a.nav-item,
   background: #2d2d2d;
   border-bottom: 1px solid #3e3e3e;
   flex-shrink: 0;
-  transition: transform 0.3s ease, opacity 0.3s ease;
+  transition: transform 0.3s ease, opacity 0.3s ease, height 0.3s ease, padding 0.3s ease, margin 0.3s ease;
   z-index: 100;
+  overflow: hidden;
 }
 
 .mobile-terminal-header.hidden {
   transform: translateY(-100%);
   opacity: 0;
   pointer-events: none;
+  height: 0;
+  padding-top: 0;
+  padding-bottom: 0;
+  margin-top: 0;
+  margin-bottom: 0;
+  border-width: 0;
+  flex-shrink: 1;
 }
 
 .mobile-terminal-header.visible {
   transform: translateY(0);
   opacity: 1;
+  height: auto;
 }
 
 .mobile-terminal-header-left,