feat(firefox): implement URL-based dynamic newtab for tridactyl

Automatically sets the newtab page based on the initial active tab URL, enabling modular per-profile configuration.

apps/firefox/default.nix

@@ -38,6 +38,9 @@
     bind J tabnext
     bind K tabprev
     unbind <C-e>
+
+    " Modular NewTab: Detect profile by initial URL and set newtab accordingly
+    js tri.browser.tabs.query({active: true, currentWindow: true}).then(tabs => { if (tabs.length > 0) { const url = tabs[0].url; if (url.includes("youtube.com")) { tri.config.set("newtab", "https://youtube.com"); } } })
   '';
 
   programs.firefox = {