Merge branch 'main' into feat/aqhi

Port to current main: main reserved layer-state token 0 for street-level, so
air-quality takes the next free token, 4 (registry, ledger, and the allocation
tests shift by one). Main moved source contracts into sourceComposition.js, so
air-quality registers its getSnapshot contract there. Package boundaries keep
main's lists plus this branch's air-quality modules and packages.

src/data/layerStateTokenReservations.json

@@ -1,5 +1,5 @@
 [
-  ["air-quality", "0"],
+  ["air-quality", "4"],
   ["ais-live-vessels", "a"],
   ["alpr-cameras", "p"],
   ["bhote-koshi-2026", "h"],
@@ -10,6 +10,7 @@
   ["earthquakes", "e"],
   ["fire-perimeters", "2"],
   ["flights", "f"],
+  ["gnss-integrity", "3"],
   ["local-dams", "q"],
   ["local-datacenters", "d"],
   ["local-firms", "w"],
@@ -20,6 +21,7 @@
   ["recent-imagery", "1"],
   ["rocket-launches", "x"],
   ["satellites", "s"],
+  ["street-level", "0"],
   ["telegeography-submarine-cables", "u"],
   ["traffic", "t"],
   ["transit", "j"],