Package weight, payload capacity and per-kg payout (ISS-045)

Packages carry a real weightKg (unit weight x count with +/-30% jitter),
plane capacity becomes maxPayloadKg instead of 6 slots, load validation
sums cargo weight against the payload, and the payout gains a per-kg part.
Loadout display shows tonnage; OpenAPI swaps CatalogEntry.capacity for
maxPayloadKg and adds PackageState.weightKg.

lib/openapi.test.ts

@@ -94,18 +94,17 @@ describe('OpenAPI spec', () => {
     const catalog = openApiSpec.components.schemas.CatalogEntry.properties;
     expect(Object.keys(catalog).sort()).toEqual([
       'burnPerKm',
-      'capacity',
       'emptyWeightKg', // v0.16.0 weighted burn model input
       'label',
       'maxFuel',
+      'maxPayloadKg', // v0.27.0 (ISS-045) — replaces the v0.12.0 slot capacity
       'model',
       'price',
       'speedKmh',
     ]);
-    for (const key of ['burnPerKm', 'emptyWeightKg', 'maxFuel', 'price', 'speedKmh'] as const) {
+    for (const key of ['burnPerKm', 'emptyWeightKg', 'maxFuel', 'maxPayloadKg', 'price', 'speedKmh'] as const) {
       expect(catalog[key].type, `CatalogEntry.${key}`).toBe('number');
     }
-    expect(catalog.capacity.type).toBe('integer'); // v0.12.0 slot capacity
     expect(catalog.model.type).toBe('string');
     expect(catalog.label.type).toBe('string');
 
@@ -140,6 +139,7 @@ describe('OpenAPI spec', () => {
       'planeId',
       'reward',
       'status',
+      'weightKg', // v0.27.0 (ISS-045) — package weight in kg
     ]);
 
     const sim = openApiSpec.components.schemas.SimState.properties;