v1.9.0

Added Firefox AI playground. Firefox exposes none of Chrome's built-in AI web APIs, so the API playground cannot demo anything there. New playground-firefox/ : a standalone Firefox add-on (not part of Comment Vibe, excluded from both store zips) with one live demo per browser.trial.ml task — zero-shot (including Comment Vibe's multilingual model), sentiment, NER, question answering, fill-mask, summarization, translation, Flan-T5, text generation and embeddings — plus model download progress, the raw runEngine output, a code sample and a "delete cached models" button. Firefox allows one engine per extension run, so switching task reloads the add-on and reopens the page on that task. Playground: Edge tab. playground/#edge shows each API's state in Microsoft Edge (Stable 155 / Dev 157): Translator and Language Detector on by default since Edge 148, Summarizer on by default in Canary/Dev, Prompt, Writer, Rewriter and Proofreader behind edge://flags on Canary/Dev (their origin trials have e