fix(compare): show SSR data on refresh; drop dead per-page comparison fetch

Refresh bug: on mount the basket is empty for a beat before it hydrates
from the URL. The fetch effect nulled comparisonData on that transient
empty urnKey, then the one-shot 'SSR covers it' skip suppressed the
refetch — leaving the page blank on reload. The effect is now gated on
isInitialized, never blanks on empty (the render already shows the empty
state when nothing is selected), and decides fetch-vs-skip by whether it
already holds each requested school's data (SSR or a prior fetch).

Perf: useComparison ran a useSWR('/api/compare') whose result nothing
consumed — dead weight that fired on every page (Navigation + Toast are
global) whenever the basket was non-empty, and duplicated ComparisonView's
own fetch on the compare page. Removed; the hook now exposes basket state
only.

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

nextjs-app/hooks/useComparison.ts

@@ -1,50 +1,18 @@
 /**
- * Custom hook for managing school comparison state
- * Uses shared context for real-time updates across components
+ * Custom hook for managing school comparison state.
+ *
+ * This hook is mounted on every page via the global Navigation and
+ * ComparisonToast, so it must stay cheap — it exposes basket state only.
+ * The compare page fetches `/api/compare` itself (ComparisonView); nothing
+ * ever read the comparison payload from here, so the previous per-page SWR
+ * fetch (which fired on every page whenever the basket was non-empty) was
+ * dead weight and has been removed.
  */
 
 'use client';
 
-import useSWR from 'swr';
-import { fetcher } from '@/lib/api';
 import { useComparisonContext } from '@/context/ComparisonContext';
-import type { ComparisonResponse } from '@/lib/types';
 
 export function useComparison() {
-  const {
-    selectedSchools,
-    addSchool,
-    removeSchool,
-    replaceSchools,
-    clearAll,
-    isSelected,
-    canAddMore,
-    isInitialized,
-  } = useComparisonContext();
-
-  // Fetch comparison data for selected schools
-  const urns = selectedSchools.map((s) => s.urn).join(',');
-  const { data, error, isLoading, mutate } = useSWR<ComparisonResponse>(
-    selectedSchools.length > 0 ? `/compare?urns=${urns}` : null,
-    fetcher,
-    {
-      revalidateOnFocus: false,
-      dedupingInterval: 10000,
-    }
-  );
-
-  return {
-    selectedSchools,
-    comparisonData: data?.comparison,
-    isLoading,
-    error,
-    addSchool,
-    removeSchool,
-    replaceSchools,
-    clearAll,
-    isSelected,
-    canAddMore,
-    isInitialized,
-    mutate,
-  };
+  return useComparisonContext();
 }