test: add memoization verification test for PageTitleInput

Adds a test to verify that fetchPageId is not called on re-renders
when dependencies (wikiUrl, debouncedPageTitle) are unchanged.

This test should fail with the current IIFE implementation because
the async IIFE executes on every render, creating a new Promise and
calling fetchPageId each time. The test proves that useMemo is
necessary for proper memoization.

Co-Authored-By: Claude

Author: Wintus

src/components/PageTitleInput.tsx

@@ -219,5 +219,28 @@ if (import.meta.vitest) {
 			);
 			expect(errorMessage).toBeInTheDocument();
 		});
+
+		it('does not call fetchPageId on re-render when dependencies are unchanged', async () => {
+			mockFetchPageId.mockResolvedValue(123);
+
+			const { rerender } = await act(async () =>
+				render(
+					<PageTitleInput initialPageTitle="Test Title" wikiUrl={stubWikiUrl} />
+				)
+			);
+
+			// Initial render should trigger one call
+			expect(mockFetchPageId).toHaveBeenCalledTimes(1);
+
+			// Re-render with same props (simulates parent re-render)
+			await act(async () =>
+				rerender(
+					<PageTitleInput initialPageTitle="Test Title" wikiUrl={stubWikiUrl} />
+				)
+			);
+
+			// Should still be 1, not 2 - memoization should prevent duplicate calls
+			expect(mockFetchPageId).toHaveBeenCalledTimes(1);
+		});
 	});
 }