Bootstrap repo with TypeScript source-of-truth and generated JSON Schema

Tracks SEP-2127 (MCP Server Cards) as an experimental extension while the SEP
itself is under review. The schema.ts is structured to be lifted directly into
schema/draft/schema.ts of the main spec when Server Cards graduate -- only the
inlined MetaObject and Icon definitions need to be removed during migration.

- schema.ts: ServerCard, Server, Repository, Remote, Package, Argument, Input,
  KeyValueInput, etc. plus inlined MetaObject and Icon
- scripts/generate-schema.ts: typescript-json-schema with 2020-12 transforms
- scripts/validate-examples.ts: ajv validator over examples/{ServerCard,Server}/
- examples/: 2 valid + 4 invalid Server Card cases, 1 valid Server case
- README: status, layout, schema URL conventions, graduation plan
- CI workflow: check + validate + format on every PR

examples/Server/valid/with-package.json

@@ -0,0 +1,27 @@
+{
+  "$schema": "https://static.modelcontextprotocol.io/schemas/v1/server.schema.json",
+  "name": "example-org/with-package",
+  "version": "0.4.2",
+  "description": "Server document with a locally-runnable npm package.",
+  "repository": {
+    "url": "https://github.com/example-org/with-package",
+    "source": "github"
+  },
+  "packages": [
+    {
+      "registryType": "npm",
+      "identifier": "@example-org/with-package",
+      "version": "0.4.2",
+      "runtimeHint": "npx",
+      "transport": { "type": "stdio" },
+      "environmentVariables": [
+        {
+          "name": "EXAMPLE_API_KEY",
+          "description": "Example API key.",
+          "isRequired": true,
+          "isSecret": true
+        }
+      ]
+    }
+  ]
+}