itinerary: add downtown and waterfront options to Sep 21

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

days/2026-09-21.md

@@ -7,6 +7,10 @@
 > Menu: [`sf_sights.md`](../sf_sights.md). Items below are agreed; everything else is still on the menu.
 
 - **Morning** BART from Daly City downtown — cable cars, Union Square, Chinatown, North Beach
+- *Optional:* Ferry Building — marketplace, food; on the way from BART (Embarcadero) to the waterfront
+- *Optional:* North Waterfront on foot or F-line streetcar after North Beach — Coit Tower, Lombard Street, Fisherman's Wharf / Pier 39 (sea lions), Ghirardelli Square
+- *Optional:* Alcatraz — ferry from Pier 33, ~2.5–3 hrs. Tickets: [alcatrazcitycruises.com](https://www.alcatrazcitycruises.com/)
+- *Optional:* Mission District (murals, Dolores Park, burritos) and Castro — neighbourhood afternoon instead of the car stops
 - **Afternoon** Car stops, optional, in route order:
 - *Optional:* Twin Peaks — city panorama, 15-min stop. Navigate to [Christmas Tree Point](https://www.google.com/maps/search/Christmas+Tree+Point+San+Francisco)
 - *Optional:* Painted Ladies — 10 min north-east; short stop at Alamo Square
@@ -16,5 +20,4 @@
 ## Notes
 
 - Silicon Valley and the Golden Gate sunset moved to [Sep 20](2026-09-20.md)
-- **Alcatraz** — ferry from Pier 33, ~2.5–3 hrs, no car needed. Tickets: [alcatrazcitycruises.com](https://www.alcatrazcitycruises.com/)
 - **Monday:** some museums (incl. the de Young, Computer History Museum) are closed