fix(search): log warning when page fetch fails during indexing

Add console.warn so that failed fetches are visible in the developer
console, making it easier to debug missing search results.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Bowl42

src/plugins/search/search.js

@@ -338,7 +338,8 @@ export async function init(config, vm) {
           await saveData(config.maxAge, expireKey);
         }
       },
-      async _error => {
+      async error => {
+        console.warn(`[Docsify] Failed to fetch ${path} for search indexing`, error);
         if (len === ++count) {
           await saveData(config.maxAge, expireKey);
         }