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/sources/reference.test.mjs

@@ -17,14 +17,17 @@ test('reference factories retain compatibility without starting acquisition or s
     'air-quality',
     'fire-perimeters',
     'cables',
+    'gnss-integrity',
   ]);
   assert.notEqual(first.earthquakes, second.earthquakes);
   assert.notEqual(first['air-quality'], second['air-quality']);
   assert.notEqual(first['fire-perimeters'], second['fire-perimeters']);
   assert.notEqual(first.cables, second.cables);
+  assert.notEqual(first['gnss-integrity'], second['gnss-integrity']);
   assert.equal(typeof first.earthquakes.getSnapshot, 'function');
   assert.equal(typeof first['air-quality'].getSnapshot, 'function');
   assert.equal(typeof first['fire-perimeters'].getSnapshot, 'function');
   assert.equal(typeof first.cables.fetch, 'function');
+  assert.equal(typeof first['gnss-integrity'].getSnapshot, 'function');
   assert.equal(requests, 0);
 });