bookings: save Yosemite cabin welcome packet PDF

Add the Sep 21 full-page printout and fill the Markdown summary with
details it was missing: approach routes, host email, cell coverage
caveat, extra house rules, supermarkets via 120/140, water outages.

bookings/stays/cabin-yosemite-wawona.md

@@ -48,3 +48,4 @@ before arrival and do not replace the saved value without confirmation. See
 - [Receipt](../../sources/stays/2026-04-05_Yosemite_Receipt_1752-9689.pdf)
 - [Booking.com chat](../../sources/stays/2026-09-16_YosemiteCabin_Booking_Chat.md)
 - [Welcome packet — door code, wifi, directions, rules](../../sources/stays/2026-09-14_Yosemite_Welcome_Packet.md)
+- [Welcome packet — full printout, Sep 21](../../sources/stays/2026-09-21_Yosemite_Welcome_Packet.pdf)