fix: jump to top on page change before post deep-link alignment

Entering /browse via a popular-section card carried ?post=, which made
ScrollToTop skip the reset entirely. The window stayed at the previous
page's bottom scroll, so the deep-link animation visibly scrolled UP from
the bottom to the target post.

Now any pathname change jumps to the top first (even with ?post=), letting
the destination align to the post by scrolling down from the top. Hash
anchors and same-page ?post= changes are still left alone.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/ScrollToTop.tsx

@@ -1,21 +1,45 @@
-import { useEffect } from "react";
+import { useEffect, useRef } from "react";
 import { useLocation } from "react-router-dom";
 
 /**
- * Resets the window to the top on every route change. React Router does not
+ * Resets the window to the top on client navigation. React Router does not
- * restore scroll on client navigation, so without this a short new page would
+ * restore scroll on its own, so without this a short new page would clamp to
- * clamp to wherever the previous (taller) page was scrolled — e.g. landing at
+ * wherever the previous (taller) page was scrolled — e.g. landing at the bottom
- * the bottom of a category page after clicking a card far down the home grid.
+ * of a category page after clicking a card far down the home grid.
  *
- * Skips navigations that carry a hash (`#post-<id>`, `#categories`, …) or a
+ * Navigating to a *different* page always jumps to the top, even when the URL
- * `?post=<id>` deep link so the target page can handle its own alignment.
+ * carries `?post=<id>`. The destination's own deep-link logic then aligns to
+ * that post by scrolling DOWN from the top, instead of animating UP from the
+ * previous page's bottom scroll — which looked like the page "scrolling up from
+ * the bottom" after tapping a popular-section card.
+ *
+ * A hash (`#post-<id>`, `#categories`, …) is left alone so the target page can
+ * handle its own anchor alignment. A same-page `?post=` change (clicking
+ * another card while already on the list) is also left alone so it doesn't
+ * fight the in-page alignment.
  */
 export function ScrollToTop() {
   const { pathname, search, hash } = useLocation();
+  const prevPathname = useRef(pathname);
 
   useEffect(() => {
-    if (hash || new URLSearchParams(search).has("post")) return;
+    const pathnameChanged = prevPathname.current !== pathname;
-    window.scrollTo({ top: 0, left: 0 });
+    prevPathname.current = pathname;
+
+    if (hash) return;
+
+    // Entering a new page: always start at the top (post deep-links align
+    // afterwards from here).
+    if (pathnameChanged) {
+      window.scrollTo({ top: 0, left: 0 });
+      return;
+    }
+
+    // Same page, search-only change (e.g. switching sort/filter): reset to top
+    // unless it's an in-page post deep-link, which handles its own alignment.
+    if (!new URLSearchParams(search).has("post")) {
+      window.scrollTo({ top: 0, left: 0 });
+    }
   }, [pathname, search, hash]);
 
   return null;