fix: use readFile instead of import attributes for JSON import

Avoids Node version compatibility issues with `with { type: "json" }`
(Node 22+) vs `assert { type: "json" }` (deprecated, errors on Node 22+).
Uses readFile with caching for the 189KB schema payload. Adds a copy
step to the build so the generated JSON lands in dist-esm/.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: raman325

package.json

@@ -38,7 +38,7 @@
     "test": "npm run generate:schema && prettier --check src && tsc --noEmit && npm run lint && tsx src/test/integration.ts",
     "generate:schema": "ts-json-schema-generator --path src/lib/incoming_message.ts --type IncomingMessage --tsconfig tsconfig.json --no-type-check --out src/lib/generated/incoming_message_schema.json",
     "prebuild": "npm run generate:schema",
-    "build": "tsc -p .",
+    "build": "tsc -p . && mkdir -p dist-esm/lib/generated && cp src/lib/generated/incoming_message_schema.json dist-esm/lib/generated/",
     "postbuild": "esm2cjs --in dist-esm --out dist-cjs -l error -t node20",
     "prepare": "npm run build",
     "prepublishOnly": "rm -rf dist-* && npm run build"

src/lib/introspect/message_handler.ts

@@ -1,10 +1,19 @@
+import { readFile } from "node:fs/promises";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
 import { UnknownCommandError } from "../error.js";
-import incomingMessageSchema from "../generated/incoming_message_schema.json" with { type: "json" };
 import { MessageHandler } from "../message_handler.js";
 import { IntrospectCommand } from "./command.js";
 import { IncomingMessageIntrospect } from "./incoming_message.js";
 import { IntrospectResultTypes } from "./outgoing_message.js";
 
+const schemaPath = join(
+  dirname(fileURLToPath(import.meta.url)),
+  "../generated/incoming_message_schema.json",
+);
+
+let cachedSchema: Record<string, unknown> | undefined;
+
 export class IntrospectMessageHandler implements MessageHandler {
   async handle(
     message: IncomingMessageIntrospect,
@@ -13,7 +22,10 @@ export class IntrospectMessageHandler implements MessageHandler {
 
     switch (message.command) {
       case IntrospectCommand.commands:
-        return incomingMessageSchema;
+        if (!cachedSchema) {
+          cachedSchema = JSON.parse(await readFile(schemaPath, "utf-8"));
+        }
+        return cachedSchema!;
       default:
         throw new UnknownCommandError(command);
     }