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

parks_sights.md

@@ -1,6 +1,6 @@
 # National Parks — Places to See
 
-*Candidate menu of sights (with seasonal notes) for the Yosemite and Sequoia / Kings Canyon legs. The chosen, day-by-day version lives in the park day plans in [`itinerary.md`](itinerary.md).*
+*Candidate menu of sights (with seasonal notes) for the Yosemite and Sequoia / Kings Canyon legs. The chosen, day-by-day version lives in [`days/`](days/) (Sep 22–26).*
 
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