feat: make grid taps preview instead of navigate on touch

On devices that can't hover, tapping an activity-strip cell now swaps
the summary below (the same action hover does on desktop) rather than
jumping straight to the article. The repointed summary link remains the
way to open the day's article.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: kt3k

src/index.page.ts

@@ -193,6 +193,14 @@ export default function (data: Lume.Data): string {
   }
   document.querySelectorAll("[data-card] [data-i]").forEach(function (cell) {
     cell.addEventListener("mouseenter", function () { show(cell); });
+    cell.addEventListener("click", function (e) {
+      // On devices that can't hover (touch), a tap previews the day instead of
+      // jumping to the article; the repointed summary link is how you open it.
+      if (window.matchMedia("(hover: none)").matches) {
+        e.preventDefault();
+        show(cell);
+      }
+    });
   });
 })();
 </script>`;