Add Payap University land as a site candidate

Payap University (Chiang Mai) is interested in leasing land to the
project; a pharmaceutical facility is under construction on the same land.

New docs/site-candidates.md puts the three options side by side (Mueang
Chi lease, Northern Region Industrial Estate, Payap) with the public facts
on Payap (Mae Khao campus on the Chiang Mai-Lampang superhighway, bought
as low-lying land, ~275 acres; Faculty of Pharmacy cosmetics production
facility tendered July 2024; RPAH cannabis/herbal bioreactor centre), why
it is attractive (5 km from the old city, a university partner with music,
pharmacy and labs, production already being built there) and the checks
that could rule it out, in order: zoning for pressing, boiler and later
electroplating; whether the university can lease to a company; the GMP
neighbour's sensitivity to our emissions (argues against biomass steam
there); flooding; plot fit; galvanics consent. Questions for the next
meeting listed. Nothing re-sited: model, RFQ and site code stay on
Mueang Chi until a plot is known.

README (intro, bullet, layout), roadmap item 9 and the lease fork in
project-timeline link to it.

docs/project-timeline.md

@@ -208,6 +208,11 @@ galvanics option alive.
 resolving before more design effort goes into the parametric model,
 because the model is only useful on one side of it.
 
+A further lease option arrived in October 2026: Payap University offers
+land in Chiang Mai next to a pharmaceutical facility under construction
+([site candidates](site-candidates.md)). Its zoning is as unverified as
+Mueang Chi's, so it adds a candidate without moving the critical path.
+
 ## The investor's CD and cassette request
 
 Adding CD and cassette to the plant has been raised by the main