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. The row is now an element with the button role:
focusable, toggled by Enter and Space, and saying whether it is expanded. A
click on its text toggles only after 500 ms, and the second press of a
double- or triple-click cancels that, so the event does not move under the
pointer while its ID is selected. A click on the caret toggles at once. The
browser test now also clicks the caret, selects the ID by dragging, by a
double-click and drag and by a triple-click, with clicks spaced as a
person's are, and uses the keyboard.

Model: opus-5-5

README.md

@@ -1365,12 +1365,13 @@ hides until the form closes, Cancel hides the form and drops what was typed, as
 does leaving the page and going back to it, and Save changes the description;
 of the recent events on the webhook page only the newest starts expanded, each
 expands and collapses, and Open leads to the event's own page; an event in the
-event log expands and collapses, and so do a delivery's attempts inside it; and
-at phone width the menu button opens and closes the mobile menu. It also fails
-if the browser reports a console warning or error, an uncaught exception, or
-anything the policy refused. `make check`
-and the image build lint it but do not run it, and `make test` leaves it out
-(its file is built only with the `browser` build tag). Run it with
+event log expands and collapses when its row's caret or its ID is clicked, and
+from the keyboard, but not when its ID is selected with the mouse, and a
+delivery's attempts inside it expand and collapse; and at phone width the menu
+button opens and closes the mobile menu. It also fails if the browser reports a
+console warning or error, an uncaught exception, or anything the policy refused.
+`make check` and the image build lint it but do not run it, and `make test`
+leaves it out (its file is built only with the `browser` build tag). Run it with
 `make test-browser` after changing `templates/` or `static/js/`: that builds
 `Dockerfile.browser`, which runs the test in a digest-pinned headless browser
 image, so the host needs no browser.