Migrate to nodenext module resolution for TS 6

TS 6 deprecates moduleResolution: "node". Switch to "nodenext"
which matches the runtime: this is an ESM Node.js app
("type": "module" with .js extensions on every import).

Side-effects of stricter ESM-aware resolution:
- ajv/dist/jtd default-import no longer works against the CJS
  module shape; switch to the named {Ajv} export.
- yaml.load returns unknown, which now propagates through
  loadSwarmAppConfig; pin its return type to SwarmAppConfig
  (the Ajv validate guard already narrows it on success).
- isolatedModules required for ts-jest under nodenext.

Author: firecow

package-lock.json

@@ -3,7 +3,7 @@ import fs from "fs";
 import {AssertionError} from "assert";
 import nunjucks from "nunjucks";
 import {JTDSchemaType} from "ajv/dist/types/jtd-schema.js";
-import Ajv from "ajv/dist/jtd.js";
+import {Ajv} from "ajv/dist/jtd.js";
 import {assertObjectOrNull} from "./asserts.js";
 
 export interface SwarmAppNetworkConfig {
@@ -180,7 +180,7 @@ export const swarmAppConfigSchema: JTDSchemaType<SwarmAppConfig> = {
     },
 };
 
-export async function loadSwarmAppConfig (configFile: string, throwOnUndefined: boolean, injectHostEnv: boolean | null = true, templatingInputFile: string | null) {
+export async function loadSwarmAppConfig (configFile: string, throwOnUndefined: boolean, injectHostEnv: boolean | null = true, templatingInputFile: string | null): Promise<SwarmAppConfig> {
     const nunjucksEnv = new nunjucks.Environment(null, {throwOnUndefined});
     const nunjucksEnvInput = injectHostEnv ? {env: process.env} : {};
     const templatingInput = yaml.load(templatingInputFile ? await fs.promises.readFile(templatingInputFile, "utf8") : "---");

src/swarm-app-config.ts

@@ -1,8 +1,8 @@
 {
   "compilerOptions": {
     "target": "ESNext",
-    "moduleResolution": "node",
-    "module": "ESNext",
+    "moduleResolution": "nodenext",
+    "module": "nodenext",
     "esModuleInterop": true,
     "forceConsistentCasingInFileNames": true,
     "inlineSourceMap": true,
@@ -11,6 +11,7 @@
     "skipLibCheck": true,
     "noUncheckedIndexedAccess": true,
     "noImplicitOverride": true,
-    "exactOptionalPropertyTypes": true
+    "exactOptionalPropertyTypes": true,
+    "isolatedModules": true
   }
 }