chore: import upstream snapshot with attribution

packages/js-sdk/tsconfig.json

@@ -0,0 +1,35 @@
+{
+  "compilerOptions": {
+    "outDir": "dist",
+    "target": "es2022",
+    "module": "esnext",
+    // Keep assignment (not `[[Define]]`) semantics for class fields. `target:
+    // es2022` would default this to `true`, which changes class-field emit and
+    // shifts stack frames — breaking the template builder's fixed-depth caller
+    // resolution (getCallerDirectory / per-step stack traces). Adopting define
+    // semantics should be a separate, deliberately tested change.
+    "useDefineForClassFields": false,
+    "lib": [
+      "dom",
+      "es2022"
+    ],
+    "sourceMap": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "strict": true,
+    "forceConsistentCasingInFileNames": true,
+    "noFallthroughCasesInSwitch": true,
+    "moduleResolution": "bundler",
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "declaration": true,
+  },
+  "include": [
+    "src"
+  ],
+  "exclude": [
+    "dist",
+    "node_modules",
+    "tsdown.config.ts"
+  ]
+}