Feature Request: Dynamic URL Placeholder in `browser.ml.chat.prompts` for Firefox AI Integration

Hi all, I’ve been experimenting with Firefox’s new AI chat integration and adding custom prompts via `about:config` using `browser.ml.chat.prompts.#`. Right now, prompt values are static JSON strings, like: ```json {"label":"Answer","id":"answer","value":"Answer selected question"} ``` This works great for fixed text, but there’s no way to dynamically include useful context like the **current page URL**. For example, I’d like to create a prompt like: ```json {"label":"Summarize w/ URL","id":"summarize_with_url","value":"Summarize this selection. Page URL: {{url}}"} ``` …but currently, `{{url}}` (or similar placeholders) isn’t supported, and the AI chat doesn’t automatically pull the page URL as context. This means I either have to manually copy/paste the URL or use a separate bookmarklet workaround, which breaks the smooth workflow. **Feature request:** * Add support for variables like `{{url}}`, `{{title}}`, or `{{selection}}` in `browser.ml.chat.prompts`. * This would make prompts far more powerful and let AI chat automatically reference page context. Has anyone found a hidden about:config trick for this, or can this be added to Firefox’s roadmap? Thanks!