Fix zod import and resolve all test failures

Create proper TypeScript wrapper for zod to avoid ESM/CommonJS interop issues.

The Problem:
- Directly importing from 'src/external/zod.js' (CommonJS) using ESM import
  syntax in TypeScript doesn't work reliably in vitest's module system
- This caused 'z' to be undefined at runtime in tests

The Solution:
- Created src/zod.ts that cleanly re-exports z from 'zod' package
- Updated src/ipc.ts to import from './zod' instead of './external/zod'
- Fixed incorrect import path in ipc.test.ts (../../utils → ../utils)

This follows the established pattern where:
1. src/external/*.js wraps the npm package (for build bundling)
2. src/*.ts provides clean TypeScript interface (for code usage)
3. Code imports from src/*.ts, never directly from src/external/*.js

Result: All 6 test suites now pass (212 tests total)!

Author: jdalton

src/ipc.ts

@@ -33,7 +33,7 @@ import { promises as fs } from 'node:fs'
 import os from 'node:os'
 import path from 'node:path'
 
-import { z } from './external/zod'
+import { z } from './zod'
 
 // Define BufferEncoding type for TypeScript compatibility.
 type BufferEncoding = globalThis.BufferEncoding

src/zod.ts

@@ -0,0 +1,6 @@
+/**
+ * @fileoverview Zod schema validation library wrapper for type-safe runtime validation.
+ * Provides access to zod's schema builder through the z object.
+ */
+
+export { z } from 'zod'

test/registry/ipc.test.ts

@@ -17,7 +17,7 @@ import {
   readIpcStub,
   writeIpcStub,
 } from '@socketsecurity/lib/ipc'
-import { runWithTempDir } from '../../utils/temp-file-helper.mts'
+import { runWithTempDir } from '../utils/temp-file-helper'
 
 describe('ipc', () => {
   describe('createIpcChannelId', () => {