fix(web): actionable empty state for the summary list

Videos rows are created by `tapir run`, not when a YouTube account is
connected, so a freshly-connected account correctly shows an empty list —
but the old empty state ("No videos yet") gave no clue why or what to do.
Split it on whether the user has any connection:

- connected, no videos: a distinct accent callout telling them to run
  `tapir run` to discover subscriptions.
- not connected: a prompt with a Connect YouTube button.

handleList fetches connections only when the list is empty. Includes
web-shot captures of all three states under docs/ux-review/fixes/.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/web/handlers.go

@@ -155,11 +155,24 @@ func (a *App) handleList(w http.ResponseWriter, r *http.Request) {
 	}
 	rows = f.apply(rows)
 
+	// hasConnected drives the empty state: a fresh account with a connection but
+	// no `tapir run` yet has zero rows, and we want it to read "connected, run
+	// tapir" rather than "nothing here". Only needed when the list is empty.
+	hasConnected := false
+	if len(rows) == 0 {
+		conns, err := a.Store.ConnectionsForUser(r.Context(), userID)
+		if err != nil {
+			a.serverError(w, r, "connections for user", err)
+			return
+		}
+		hasConnected = len(conns) > 0
+	}
+
 	if isHTMX(r) {
-		a.render(w, r, summaryList(rows))
+		a.render(w, r, summaryList(rows, hasConnected))
 		return
 	}
-	a.render(w, r, ListPage(rows, f, takeFlash(w, r)))
+	a.render(w, r, ListPage(rows, f, takeFlash(w, r), hasConnected))
 }
 
 // handleDetail renders one summary in full (highlights, takeaways, action group).