chore(blog): guard keydown for IME composition and <select>

Code review forward-proofing:
- Early-return on event.isComposing so the / shortcut doesn't disrupt
  IME composition (multi-keystroke input methods).
- Treat <select> as editable so / doesn't steal focus while a dropdown
  is open and the user is typing to seek.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/molecules/BlogSearch.astro

@@ -146,12 +146,14 @@
     // contenteditable element). `Esc` while the input is focused clears the
     // query, blurs, and restores the full archive.
     document.addEventListener("keydown", (event) => {
+      if (event.isComposing) return;
       if (event.key === "/" && !event.metaKey && !event.ctrlKey && !event.altKey) {
         const target = event.target as HTMLElement | null;
         const tag = target?.tagName;
         const editable =
           tag === "INPUT" ||
           tag === "TEXTAREA" ||
+          tag === "SELECT" ||
           target?.isContentEditable === true;
         if (!editable) {
           event.preventDefault();