itinerary: split day plans into days/, plan SF Sep 21

- One file per day under days/; timeline table reduced to date, weekday, place
- Sep 19–20: KT & VT Uber to Airbnb, rest day; LK & MS drive rental to Airbnb
- Sep 21: Silicon Valley morning, optional Twin Peaks / Painted Ladies /
  Lands End, Battery Spencer at sunset
- LK Hertz LAX rental marked not available for planning; LA / San Diego
  hotels cancelled
- sf_sights: add Silicon Valley and Mission / Castro, skip Computer History
  Museum

Claude-Session: https://claude.ai/code/session_01CWLR7htYGAB9i89P8jCCLn

README.md

@@ -4,7 +4,8 @@ Group trip: SF → Yosemite → Sequoia → LA → Las Vegas → SF.
 
 ## Structure
 
-- [`itinerary.md`](itinerary.md) — full plan: timeline, day-by-day, bookings overview
+- [`itinerary.md`](itinerary.md) — bookings overview and timeline
+- [`days/`](days/) — one file per day: logistics, agreed plan, notes
 - [`expenses.md`](expenses.md) — shared-expense ledger and reconciliation notes
 - [`bookings/stays/`](bookings/stays/) — one Markdown summary per accommodation booking
 - [`bookings/transport/`](bookings/transport/) — one Markdown summary per flight or car booking