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

README.md

@@ -1353,15 +1353,16 @@ of its description and 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
-`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.
+event's own page; an event in the 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.
 
 The package's tarball is committed as `3p/alpinejs-csp-3.14.9.tgz`, byte for
 byte as the npm registry publishes it. It is a dependency, not this repo's build