chore(spec-api): scaffold @uatu/spec package metadata

TypeScript 5.6 with strict mode, bundler module resolution. Tests
run via node --test --experimental-strip-types so we don't need
vitest or a build step. Adds node_modules to .gitignore.

pkg/spec-api/tsconfig.json

@@ -0,0 +1,19 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "noImplicitOverride": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "lib": ["ES2020"],
+    "types": ["node"],
+    "noEmit": true,
+    "allowImportingTsExtensions": true
+  },
+  "include": ["src/**/*.ts", "test/**/*.ts"]
+}