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

package.json

@@ -0,0 +1,22 @@
+{
+  "name": "@modelcontextprotocol/experimental-ext-server-card",
+  "version": "0.0.0",
+  "private": true,
+  "description": "Experimental schema for SEP-2127 (MCP Server Cards). See README for status and graduation plan.",
+  "type": "module",
+  "scripts": {
+    "generate": "tsx scripts/generate-schema.ts",
+    "check": "tsx scripts/generate-schema.ts --check && tsc --noEmit",
+    "validate": "tsx scripts/validate-examples.ts",
+    "format": "prettier --write \"**/*.{ts,json,md}\"",
+    "format:check": "prettier --check \"**/*.{ts,json,md}\""
+  },
+  "devDependencies": {
+    "ajv": "^8.18.0",
+    "ajv-formats": "^3.0.1",
+    "prettier": "^3.6.2",
+    "tsx": "^4.21.0",
+    "typescript": "^5.6.2",
+    "typescript-json-schema": "^0.67.1"
+  }
+}