Event log: only the newest event expanded, and only the 50 most recent (closes #349)

The event log now loads the 50 newest events in its query and opens
only the newest on load, as the recent events on a webhook's page
already do. With 50 at most there is never a second page, so paging is
gone: the page links, the `page` query parameter, the page number that
Replay and Resubmit carried back to the log, and `pageOrFirst` with its
test. The count beside the heading reads "50 most recent of N events"
when there are more. The comments and README lines that named `page` as
the query parameter the service reads now name `next` and `notice`.

Model: opus-5-5

internal/server/alpine_browser_test.go

@@ -765,14 +765,15 @@ func checkRecentEvents(ctx context.Context, t *testing.T, url string) {
 		"the event's own page does not show its body")
 }
 
-// checkEventLog loads the event log and checks an event's row. Clicking
-// its ID expands the event, and in there clicking its delivery shows the
-// delivery's attempts and clicking again hides them. Clicking the row's
-// caret collapses the event, clicking it again expands it, and clicking
-// the ID again collapses it. While the event is expanded the row says so
-// and its caret is turned up, and while it is collapsed neither. It then
-// runs checkEventSelection on the log's last event, lastEventID, and
-// checkEventKeyboard on eventID.
+// checkEventLog loads the event log and checks that of its events only
+// the newest, eventID, starts expanded: its row says so and its caret is
+// turned up, and the log's last event, lastEventID, starts collapsed. In
+// the newest event, clicking its delivery shows the delivery's attempts
+// and clicking again hides them. Clicking the row's caret collapses the
+// event, clicking it again expands it, clicking its ID collapses it and
+// clicking the ID again expands it. While the event is collapsed the row
+// says so and its caret is turned down. It then runs checkEventSelection
+// on lastEventID and checkEventKeyboard on eventID.
 func checkEventLog(
 	ctx context.Context,
 	t *testing.T,
@@ -790,20 +791,19 @@ func checkEventLog(
 	caretUp := caret + `[contains(@class, "rotate-180")]`
 	caretDown := caret + `[not(contains(@class, "rotate-180"))]`
 	expanded := `form[action$="/` + eventID + `/resubmit"]`
+	lastExpanded := `form[action$="/` + lastEventID + `/resubmit"]`
 	deliveryRow := `//span[text()="` + targetName + `"]`
 	attempt := `//span[text()="Attempt 1"]`
 
 	require.NoError(t, chromedp.Run(ctx, loadPage(url)))
 
-	assert.True(t, hidden(ctx, expanded), "the event starts expanded")
-
-	click(ctx, t, id)
-	assert.True(t, shown(ctx, expanded),
-		"clicking the event's ID does not expand it")
+	assert.True(t, shown(ctx, expanded), "the newest event starts collapsed")
 	assert.True(t, shown(ctx, row+`[@aria-expanded="true"]`),
 		"the expanded event's row does not say it is expanded")
 	assert.True(t, shown(ctx, caretUp),
 		"the expanded event's caret does not turn up")
+	assert.True(t, hidden(ctx, lastExpanded),
+		"an older event starts expanded")
 
 	assert.True(t, hidden(ctx, attempt), "the delivery's attempts start shown")
 
@@ -829,7 +829,11 @@ func checkEventLog(
 
 	click(ctx, t, id)
 	assert.True(t, hidden(ctx, expanded),
-		"clicking the event's ID again does not collapse it")
+		"clicking the event's ID does not collapse it")
+
+	click(ctx, t, id)
+	assert.True(t, shown(ctx, expanded),
+		"clicking the event's ID again does not expand it")
 
 	checkEventSelection(ctx, t, url, lastEventID)
 	checkEventKeyboard(ctx, t, url, eventID)
@@ -878,8 +882,11 @@ func checkEventSelection(
 		`window.getSelection().removeAllRanges()`, nil,
 	)
 
+	// The newest event starts expanded, which can push this one below
+	// the short window, where the mouse cannot reach it.
 	require.NoError(t, chromedp.Run(
 		ctx, chromedp.EmulateViewport(shortWidth, shortHeight), loadPage(url),
+		chromedp.ScrollIntoView(id, chromedp.BySearch),
 	))
 
 	selectText(ctx, t, id)
@@ -922,8 +929,9 @@ func checkEventSelection(
 }
 
 // checkEventKeyboard loads the event log and checks that Tab from the
-// page's Back link reaches the event's row, the first after it, and that
-// Enter then expands the event and Space collapses it.
+// page's Back link reaches the row of the newest event, the first after
+// it, and that Enter then collapses that event, which starts expanded,
+// and Space expands it again.
 func checkEventKeyboard(
 	ctx context.Context, t *testing.T, url, eventID string,
 ) {
@@ -945,10 +953,10 @@ func checkEventKeyboard(
 		"Tab from the Back link does not reach the event's row")
 
 	require.NoError(t, chromedp.Run(ctx, chromedp.KeyEvent(kb.Enter)))
-	assert.True(t, shown(ctx, expanded), "Enter does not expand the event")
+	assert.True(t, hidden(ctx, expanded), "Enter does not collapse the event")
 
 	require.NoError(t, chromedp.Run(ctx, chromedp.KeyEvent(" ")))
-	assert.True(t, hidden(ctx, expanded), "Space does not collapse the event")
+	assert.True(t, shown(ctx, expanded), "Space does not expand the event")
 }
 
 // selectText selects the text of the element matching an XPath