Milestone 0: import zappier billing, Verae middleware, and Zapier research

Compose-ready workspace: packages/zappier (rate card, portal, Stripe),
packages/verae-zapier-middleware (timestamp + NATS), packages/verae-zapier
(CLI app), vendor/zapier-platform, and research/zapier vendor corpus.

Gate 0 structure checks pass. Product code and research are not yet wired.

vendor/zapier-platform/packages/schema/lib/schemas/FieldDynamicChoicesSchema.js

@@ -0,0 +1,54 @@
+'use strict';
+
+const makeSchema = require('../utils/makeSchema');
+
+const FunctionSchema = require('./FunctionSchema');
+const RequestSchema = require('./RequestSchema');
+
+module.exports = makeSchema(
+  {
+    id: '/FieldDynamicChoicesSchema',
+    description:
+      'Describes dynamic dropdowns powered by a perform function or request.',
+    type: 'object',
+    required: ['perform'],
+    properties: {
+      perform: {
+        description:
+          'A function or request that returns choices for this dynamic dropdown.',
+        oneOf: [{ $ref: FunctionSchema.id }, { $ref: RequestSchema.id }],
+      },
+    },
+    additionalProperties: false,
+    examples: [
+      { perform: '$func$0$f$' },
+      { perform: { source: 'return []' } },
+      {
+        perform: {
+          method: 'GET',
+          url: 'https://api.example.com/choices',
+        },
+      },
+    ],
+    antiExamples: [
+      {
+        example: {},
+        reason: 'Missing required key: perform',
+      },
+      {
+        example: { someKey: 'value' },
+        reason: 'Missing required key: perform',
+      },
+      {
+        example: { perform: 'invalid' },
+        reason:
+          'Invalid value for key: perform (must be a function or request)',
+      },
+      {
+        example: { perform: '$func$0$f$', unknownKey: 'value' },
+        reason: 'Invalid extra property: unknownKey',
+      },
+    ],
+  },
+  [FunctionSchema, RequestSchema],
+);