fix(compare): keep the add-school sheet above the on-screen keyboard

The bottom-sheet overlay was position:fixed inset:0, sized to the LAYOUT
viewport, so when the mobile keyboard opened it kept full height: the
sheet (anchored to the overlay's bottom) and the lower half of the dim
backdrop sat behind the keyboard, hiding the search input and results.

Track window.visualViewport (height + offsetTop) while the modal is open
and pin the overlay to the visible region, so backdrop and sheet stay
above the keyboard. Size the sheet against the overlay (max-height:100%,
min-height:min(55vh,100%)) instead of vh, and drop the results list's own
inner scroll on mobile so the sheet is a single scroll area.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

nextjs-app/components/Modal.tsx

@@ -5,7 +5,7 @@
 
 'use client';
 
-import { useEffect, useCallback } from 'react';
+import { useEffect, useCallback, useRef } from 'react';
 import { createPortal } from 'react-dom';
 import styles from './Modal.module.css';
 
@@ -18,6 +18,8 @@ interface ModalProps {
 }
 
 export function Modal({ isOpen, onClose, children, title, size = 'medium' }: ModalProps) {
+  const overlayRef = useRef<HTMLDivElement>(null);
+
   const handleEscape = useCallback((e: KeyboardEvent) => {
     if (e.key === 'Escape') {
       onClose();
@@ -39,6 +41,32 @@ export function Modal({ isOpen, onClose, children, title, size = 'medium' }: Mod
     };
   }, [isOpen, handleEscape]);
 
+  // Pin the overlay to the VISUAL viewport, not the layout viewport. On mobile
+  // the on-screen keyboard shrinks the visual viewport but not the layout one,
+  // so a `position: fixed; inset: 0` overlay keeps full height — leaving the
+  // bottom-anchored sheet (and the dim backdrop's lower half) hidden behind
+  // the keyboard. Tracking visualViewport.height/offsetTop keeps the whole
+  // overlay — backdrop and sheet — inside the visible area, above the keyboard.
+  useEffect(() => {
+    if (!isOpen) return;
+    const vv = typeof window !== 'undefined' ? window.visualViewport : null;
+    const el = overlayRef.current;
+    if (!vv || !el) return;
+
+    const sync = () => {
+      el.style.top = `${vv.offsetTop}px`;
+      el.style.height = `${vv.height}px`;
+      el.style.bottom = 'auto';
+    };
+    sync();
+    vv.addEventListener('resize', sync);
+    vv.addEventListener('scroll', sync);
+    return () => {
+      vv.removeEventListener('resize', sync);
+      vv.removeEventListener('scroll', sync);
+    };
+  }, [isOpen]);
+
   if (!isOpen || typeof window === 'undefined') return null;
 
   const handleOverlayClick = (e: React.MouseEvent) => {
@@ -48,7 +76,7 @@ export function Modal({ isOpen, onClose, children, title, size = 'medium' }: Mod
   };
 
   return createPortal(
-    <div className={styles.overlay} onClick={handleOverlayClick}>
+    <div ref={overlayRef} className={styles.overlay} onClick={handleOverlayClick}>
       <div className={`${styles.modal} ${styles[size]}`}>
         <div className={styles.header}>
           {title && <h2 className={styles.title}>{title}</h2>}