docs: surface Kijiji AND-matching behavior in tool, API, and MCP responses

Kijiji zero-result queries (e.g. 'macbook air m1 apple silicon') are
confusing because the failure mode is non-obvious. Surface the root
cause everywhere the caller can see it:
- MCP tool description warns about AND-matching and gives a concrete
  before/after example
- API 404 body includes the actionable hint via emptySearchResponse(hint)
- Core scraper logs the built URL and tip on page-1 zero results
- MCP handler unwraps the API message field so the hint reaches the LLM

packages/core/src/scrapers/kijiji.ts

@@ -893,7 +893,17 @@ export default async function fetchKijijiItems(
 
     const searchResults = parseSearch(searchHtml, BASE_URL);
     if (searchResults.length === 0) {
-      logger.log(`No more results found on page ${page}. Stopping pagination.`);
+      if (page === 1) {
+        logger.log(
+          `No results found on page 1. The search URL was: ${searchUrl}\n` +
+            `Tip: Kijiji matches ALL words in the query against listing titles. ` +
+            `Try a shorter or more common query (e.g. "macbook air m1" instead of "macbook air m1 apple silicon").`,
+        );
+      } else {
+        logger.log(
+          `No more results found on page ${page}. Stopping pagination.`,
+        );
+      }
       break;
     }