GHSA-FWQX-8365-9983 Algernon: Single-file mode unconditionally enables debug mode

Summary When Algernon is invoked with a single file path instead of a directory — the documented "quick demo" workflow algernon foo.lua, algernon page.po2, algernon index.html, algernon mywebsite.alg — singleFileMode is set to true and debugMode is forcibly enabled with no opt-out: go //...