Stored rankings file name

Stored source file name for each OpenRouter rankings section in the digest. rankings_daily stores rankings_daily.json. rankings_tool_calling and rankings_image_output store no file name, so they stay off this page. The label is the stored section name. The value is the stored file string. The bar is full when a file name is stored. The bar is not a score. This is the file name, not the row count and not the day count. A section with no stored file name stays off the page.