Event log: an event's ID can be selected without toggling it (closes #348)

An event's row in the event log was a button element, whose text a browser
does not let be selected, and a drag over the event's ID toggled the event.
The row is now an element with the button role: focusable, toggled by Enter
and Space, and saying whether it is expanded. A click that ends a text
selection leaves the event as it is. The browser test now also clicks the
row's caret, selects the ID with the mouse, and uses the keyboard.

Model: opus-5-5

static/js/app.js

@@ -82,6 +82,13 @@ document.addEventListener("alpine:init", function () {
             toggle() {
                 this.open = !this.open;
             },
+            // Toggles, except on a click that ends a text selection, such
+            // as selecting an event's ID to copy it.
+            toggleUnlessSelecting() {
+                if (window.getSelection().toString() === "") {
+                    this.toggle();
+                }
+            },
             get closed() {
                 return !this.open;
             },