feat(config): add @bytelyst/config package

- Zod-based baseEnvSchema (PORT, HOST, NODE_ENV, CORS_ORIGIN, SERVICE_NAME, COSMOS_*)
- loadConfig() with extension support for service-specific fields
- loadProductIdentity() reads product.json or falls back to env vars
- getProductId() convenience function
- Replaces 5 duplicated product-config.ts files across LysnrAI
- Peer dep: zod >=3.20.0

packages/config/package.json

@@ -0,0 +1,21 @@
+{
+  "name": "@bytelyst/config",
+  "version": "0.1.0",
+  "type": "module",
+  "exports": {
+    ".": {
+      "import": "./dist/index.js",
+      "types": "./dist/index.d.ts"
+    }
+  },
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "files": ["dist"],
+  "scripts": {
+    "build": "tsc",
+    "test": "vitest run"
+  },
+  "peerDependencies": {
+    "zod": ">=3.20.0"
+  }
+}

packages/config/src/base-schema.ts

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+/**
+ * Base environment schema shared by all Fastify microservices.
+ * Each service extends this with its own fields via loadConfig().
+ */
+
+import { z } from "zod";
+
+export const baseEnvSchema = z.object({
+  PORT: z.coerce.number().default(3000),
+  HOST: z.string().default("0.0.0.0"),
+  NODE_ENV: z
+    .enum(["development", "production", "test"])
+    .default("development"),
+  CORS_ORIGIN: z.string().optional(),
+  SERVICE_NAME: z.string(),
+  COSMOS_ENDPOINT: z.string().min(1, "COSMOS_ENDPOINT is required"),
+  COSMOS_KEY: z.string().min(1, "COSMOS_KEY is required"),
+  COSMOS_DATABASE: z.string().default("lysnrai"),
+});
+
+export type BaseEnv = z.infer<typeof baseEnvSchema>;

packages/config/src/index.ts

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+export { baseEnvSchema, type BaseEnv } from "./base-schema.js";
+export { loadConfig } from "./loader.js";
+export {
+  loadProductIdentity,
+  getProductId,
+  _resetProductIdentity,
+  type ProductIdentity,
+} from "./product-identity.js";

packages/config/src/loader.ts

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+/**
+ * Config loader — parses process.env against the base schema + any extensions.
+ */
+
+import { z, type ZodRawShape } from "zod";
+import { baseEnvSchema } from "./base-schema.js";
+
+/**
+ * Load and validate environment configuration.
+ *
+ * @param extension - Additional Zod fields specific to this service
+ * @returns Parsed and validated config object
+ *
+ * @example
+ * ```ts
+ * const config = loadConfig({
+ *   STRIPE_SECRET_KEY: z.string().min(1),
+ *   BILLING_INTERNAL_KEY: z.string().optional(),
+ * });
+ * ```
+ */
+export function loadConfig<T extends ZodRawShape>(extension?: T) {
+  const schema = extension ? baseEnvSchema.extend(extension) : baseEnvSchema;
+  return schema.parse(process.env) as z.infer<typeof baseEnvSchema> &
+    (T extends ZodRawShape ? z.infer<z.ZodObject<T>> : Record<string, never>);
+}

packages/config/src/product-identity.ts

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+/**
+ * Product identity — reads from a product.json file or falls back to env vars.
+ * Eliminates the need for hardcoded product-config.ts files in every service.
+ */
+
+import { readFileSync } from "node:fs";
+import { resolve } from "node:path";
+
+export interface ProductIdentity {
+  productId: string;
+  displayName: string;
+  licensePrefix: string;
+  configDirName: string;
+  envVarPrefix: string;
+  bundleIdSuffix: string;
+  packageName: string;
+}
+
+let _cached: ProductIdentity | null = null;
+
+/**
+ * Load product identity from a JSON file or environment variables.
+ *
+ * @param jsonPath - Path to product.json (optional, tries common locations)
+ * @returns Product identity object
+ */
+export function loadProductIdentity(jsonPath?: string): ProductIdentity {
+  if (_cached) return _cached;
+
+  // Try loading from file
+  const paths = jsonPath
+    ? [jsonPath]
+    : [
+        resolve("shared/product.json"),
+        resolve("../shared/product.json"),
+        resolve("../../shared/product.json"),
+      ];
+
+  for (const p of paths) {
+    try {
+      const raw = readFileSync(p, "utf-8");
+      _cached = JSON.parse(raw) as ProductIdentity;
+      return _cached;
+    } catch {
+      // Try next path
+    }
+  }
+
+  // Fallback to env vars / defaults
+  _cached = {
+    productId: process.env.PRODUCT_ID || "lysnrai",
+    displayName: process.env.DISPLAY_NAME || "LysnrAI",
+    licensePrefix: process.env.LICENSE_PREFIX || "LYSNR",
+    configDirName: process.env.CONFIG_DIR_NAME || ".LysnrAI",
+    envVarPrefix: process.env.ENV_VAR_PREFIX || "LYSNR",
+    bundleIdSuffix: process.env.BUNDLE_ID_SUFFIX || "LysnrAI",
+    packageName: process.env.PACKAGE_NAME || "lysnrai",
+  };
+  return _cached;
+}
+
+/**
+ * Convenience: get just the product ID string.
+ */
+export function getProductId(): string {
+  return loadProductIdentity().productId;
+}
+
+/**
+ * Reset the cache (useful for testing).
+ * @internal
+ */
+export function _resetProductIdentity(): void {
+  _cached = null;
+}

packages/config/tsconfig.json

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+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "dist",
+    "rootDir": "src"
+  },
+  "include": ["src"],
+  "exclude": ["src/**/*.test.ts"]
+}