fix: Sticky file headers sit below review header using CSS variable

Sets --review-header-h on the card wrapper from measured header height.
FileCard reads it for sticky top offset so file headers dock just below
the review header instead of overlapping it.

apps/web/src/components/review/FileCard.tsx

@@ -82,7 +82,8 @@ export function FileCard({
     <div className="rounded-lg border border-border overflow-hidden">
       {/* File header — sticky so it stays visible when scrolling */}
       <button
-        className={`sticky top-0 z-10 flex w-full items-center gap-2 px-3 py-2 bg-muted hover:bg-muted/90 text-left text-sm font-mono transition-colors ${leftBorderClass[file.changeType]}`}
+        className={`sticky z-10 flex w-full items-center gap-2 px-3 py-2 bg-muted hover:bg-muted/90 text-left text-sm font-mono transition-colors ${leftBorderClass[file.changeType]}`}
+        style={{ top: 'var(--review-header-h, 0px)' }}
         onClick={() => setExpanded(!expanded)}
       >
         {expanded ? (

apps/web/src/components/review/ReviewTab.tsx

@@ -323,7 +323,10 @@ export function ReviewTab({ initiativeId }: ReviewTabProps) {
   }
 
   return (
-    <div className="rounded-lg border border-border bg-card">
+    <div
+      className="rounded-lg border border-border bg-card"
+      style={{ '--review-header-h': `${headerHeight}px` } as React.CSSProperties}
+    >
       {/* Header: phase selector + toolbar */}
       <ReviewHeader
         ref={headerRef}