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.ts

@@ -106,7 +106,7 @@ export const openApiSpec = {
       post: {
         summary: 'Load a package onto a plane',
         description:
-          'Bind an OPEN package to a GROUNDED ("available") plane at the package\'s origin (v0.12.0). The plane needs a free slot — capacity per catalog model; expired packages still occupy theirs. The sim clock is ticked first, so the returned snapshot reflects current game time.',
+          'Bind an OPEN package to a GROUNDED ("available") plane at the package\'s origin (v0.12.0). The plane needs enough payload room for the package weight — maxPayloadKg per catalog model; expired packages still occupy theirs (v0.27.0). The sim clock is ticked first, so the returned snapshot reflects current game time.',
         operationId: 'loadPackage',
         parameters: [
           { name: 'id', in: 'path', required: true, schema: { type: 'string' } },
@@ -461,9 +461,9 @@ export const openApiSpec = {
           burnPerKm: { type: 'number', description: 'Cruise fuel burn at a full tank, liters/km (v0.16.0 weighted model calibrates to this).' },
           emptyWeightKg: { type: 'number', description: 'Operating empty weight, kg — with burnPerKm and maxFuel it drives the v0.16.0 weight-proportional burn model.' },
           speedKmh: { type: 'number', description: 'Cruise speed, km/h.' },
-          capacity: { type: 'integer', description: 'Cargo slot capacity — packages that can be loaded on one plane (v0.12.0).' },
+          maxPayloadKg: { type: 'number', description: 'Max payload in kg — total package weight that can be loaded on one plane (v0.27.0, replaces the v0.12.0 slot count).' },
         },
-        required: ['model', 'label', 'price', 'maxFuel', 'burnPerKm', 'emptyWeightKg', 'speedKmh', 'capacity'],
+        required: ['model', 'label', 'price', 'maxFuel', 'burnPerKm', 'emptyWeightKg', 'speedKmh', 'maxPayloadKg'],
       },
       AccountState: {
         type: 'object',
@@ -498,7 +498,7 @@ export const openApiSpec = {
       LoadPackageRequest: {
         type: 'object',
         properties: {
-          planeId: { type: 'string', description: 'A GROUNDED ("available") plane at the package\'s origin with a free slot.' },
+          planeId: { type: 'string', description: 'A GROUNDED ("available") plane at the package\'s origin with enough payload room for it (v0.27.0).' },
         },
         required: ['planeId'],
       },
@@ -618,6 +618,7 @@ export const openApiSpec = {
           reward: { type: 'number' },
           cargoType: { type: 'string' },
           cargoCount: { type: 'integer' },
+          weightKg: { type: 'number', description: 'Package weight in kg (v0.27.0) — drives load validation and the per-kg payout part.' },
           deadlineSimTime: { type: 'integer', description: 'Sim-clock epoch ms (game time)' },
           // 'expired' = an open OR loaded package whose deadline passed on a tick;
           // loaded expired packages keep their slot, deliver no reward, abandon free.
@@ -634,6 +635,7 @@ export const openApiSpec = {
           'reward',
           'cargoType',
           'cargoCount',
+          'weightKg', // v0.27.0 (ISS-045) — package weight in kg
           'deadlineSimTime',
           'status',
           'planeId',