Move verse selector to htmx

assets/js/router.js

@@ -37,8 +37,20 @@
     // out of the response itself.
     this.restore =
       this.request.headers.get('HX-History-Restore-Request') === 'true';
+    // The address the page making this request is showing. htmx stamps it on
+    // everything it sends; a navigation carries nothing, because there is no
+    // page yet. It is how a handler answering the chrome -- which htmx never
+    // swaps, and which therefore outlives the page it was rendered for -- can
+    // still find out which page that is.
+    this.current = this.request.headers.get('HX-Current-URL');
   }
 
+  // That address as a URL, resolved against this request's own so a relative
+  // one still works. Null when there was no page.
+  Call.prototype.currentUrl = function () {
+    return this.current ? new URL(this.current, this.url) : null;
+  };
+
   Call.prototype.form = function () {
     return this.request.formData();
   };