Add scripts/validate-structure.js validation script

.github/workflows/validate.yml

@@ -0,0 +1,28 @@
+name: Validate GAP Structure
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  validate:
+    name: Validate GAP directories
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: "24"
+          cache: "npm"
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Validate GAP structure
+        run: npm run test:structure

metadata.schema.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://raw.githubusercontent.com/graphql/gaps/main/metadata.schema.json",
+  "title": "GAP Metadata",
+  "type": "object",
+  "properties": {
+    "title": { "type": "string" },
+    "status": { "type": "string", "enum": ["proposal", "draft", "accepted"] },
+    "authors": { "type": "array", "items": { "type": "string" } },
+    "sponsor": { "type": "string" },
+    "discussion": { "type": "string" },
+    "id": { "type": "integer" },
+    "related": { "type": "array", "items": { "type": "integer" } },
+    "replaces": { "type": "integer" },
+    "supersededBy": { "type": "integer" },
+    "tags": { "type": "array", "items": { "type": "string" } }
+  },
+  "required": ["id", "title", "status", "authors", "sponsor", "discussion"],
+  "additionalProperties": false
+}