itinerary: drop Alcatraz sold-out warning

Claude-Session: https://claude.ai/code/session_01SQPbfX7jyTALGYxJw36hbT

sf_sights.md

@@ -15,7 +15,7 @@
 - **Fisherman's Wharf / Pier 39** — sea lions
 - **Ghirardelli Square** — chocolate + waterfront dining
 - **Coit Tower** — city + bay views from Telegraph Hill
-- **Alcatraz** — ferry from Pier 33, ~2.5–3 hrs round trip. *Book weeks ahead — sells out*
+- **Alcatraz** — ferry from Pier 33, ~2.5–3 hrs round trip. Tickets: [alcatrazcitycruises.com](https://www.alcatrazcitycruises.com/)
 
 ## Downtown / Central